Bariatric equipment refers to medical devices designed for bariatric (obese) patients. Bariatric equipment is designed specifically to meet needs of these patients, meaning they can handle heavier loads, have more robust supports, and are designed with wider widths to ensure patient comfort. Nearly all medical furniture, from chairs and beds to crutches and walkers can be designed for bariatric patients.

In healthcare, “bariatric” refers to equipment designed specifically for patients whose body weight exceeds the standard limits of regular medical devices. Bariatric equipment typically features reinforced frames, wider surfaces, and increased weight capacity often exceeding 500 pounds.

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Automotive displays in the past were designed to be embedded and protected by the IP cluster within the dashboard, but increases in the amount and types of data users require has led to a greater number of display options, including Driver Information Displays (DID), Center Stack Displays (CSD) or Center Information Displays (CID), Driver Monitoring Systems (DMS) and Head-Up Displays (HUD). As electronic displays increase in size and proximity to the windshield, there is an increased need for greater impact resistance.

Additionally, there is a visible trend that automotive display design is following smartphone design towards narrow border/bond line design. This results in less bonding area between the housing and lens while display sizes are increasing (higher weight and more stress on the bond area). Meeting the automotive industry head impact test (HIT) and rear impact tests are critical requirements for automotive display bonding applications.

In this article, several impact requirements (including HIT and rear impact) have been investigated to explain how 3M VHB Tapes can help meet these critical test requirements. Specifically, display lens bonding will be examined with different impact event types as well as further aspects that are key for a reliable bond.

Automotive Display Specifications and Challenges to Material Suppliers

As automotive displays are becoming larger and closer to the windshield, higher temperature requirements are needed for the display components along with stronger, but still flexible, bond joints. Additionally, narrow bond line design is reducing the effective bonding area which results in the need for high performance bonding solutions for this application.

Automotive display impact is characterized by a brief, but high impulse on the display assembly components – 50G is a typical test level. For the adhesive bond between the display lens and housing (surrounding attachment of the lens to the housing/die-cast), a material needs to be chosen which survives all the impact forces, but is still flexible enough to:

• compensate the mismatch between both components (due to manufacturing tolerances).
• compensate the thermal expansion of dissimilar materials (with different CTEs).
• compensate and absorb vibration and shock.
• dissipate impact energy (“head form” impact and rear impact).

3M VHB Tapes

3M VHB Tapes (VHB Tapes) are double-sided, pressure sensitive adhesive (PSA) acrylic foam tapes. These tapes are characterized by having a viscoelastic conformable acrylic foam core with acrylic PSA skins. The acrylic foam provides energy absorption and stress relaxation properties that are beneficial for absorbing impact energy and reducing fatigue on sensitive electronic components due to vibration and differential thermal expansion of dissimilar materials (e.g. glass and metal).

Viscoelastic materials like VHB Tape are characterized by having a modulus and ultimate strength that is strain rate or time dependent. Fast strain rates will exhibit increased modulus and ultimate strength values when compared to slower strain rates.

An impact is representative of a fast strain rate, while differential thermal expansion of dissimilar materials due to temperature change (e.g., glass bonded to metal or plastic) will result in a slow strain rate. The curves below illustrate a high tensile strain rate (550 in/sec) compared to a quasi-static slow tensile strain rate (0.024 in/sec). The viscoelastic properties of VHB Tape are clearly shown by the very high ultimate strength associated with the fast strain rate and the significantly lower strength associated with the slow strain rates where stress relaxation is very evident.

These tapes are used in many applications requiring strong yet flexible bonds where long-term durability is required (e.g., trailer skin bonding and exterior building panel bonding). The main benefits and performance attributes of 3M VHB Tapes are summarized below:

1. Impact Resistance (tensile, compression and shear)
2. Mismatch Compensation (gap filling) — including stress relaxation
3. Thermal (differential thermal expansion and heat resistance) — including stress relaxation
4. Vibration Resistance (cyclic fatigue) — tensile fatigue from existing 3M VHB Tapes (GPH)
5. Bonding and Sealing (closed-cell construction) — IPXX testing
6. Long-term Durability (all-acrylic chemistry) — UV resistance

Role of Finite Element Analysis

The demands and requirements for automotive display manufacturers are ever-increasing in terms of both complexity and shorter time to delivery. The making of actual prototypes for a new design is time-consuming and costly and may not even be feasible or practical in the early design stages. Finite element analysis (FEA) is a tool now being used to predict the behavior and performance of automotive display assemblies and materials when no prototypes are available for testing and analysis.

To perform FEA modeling, the assembly material mechanical properties need to be properly characterized. To characterize the mechanical properties of these materials, specific tests need to be performed which correlate to the real application loads. For impact resistance, depending on the force impact direction, either tensile, compression or shear tests are performed. This established test data is transformed into a material data card which is used in the FEA modeling tool (e.g. Abaqus). In order to validate the material data card, FEA simulations are performed and then compared with the real test data.

Once simulation and real test data are comparable, FEA modeling can be used as a powerful predictive engineering tool to simulate different test parameters in an actual impact event before building a prototype. This is a significant benefit to the auto display designer and can accelerate the design and development process as well as reduce costs.

FEA Modeling of Automotive Display Applications

3M VHB Tapes have been commercially available since 1980 and the performance and durability of this acrylic foam tape family has been proven over many years in many demanding applications, such as exterior architectural panel bonding and trailer skin bonding. The use of these tapes for automotive display bonding applications is relatively new due to the recent increased use of displays and their location in automobiles. To advance the acceptance and understanding of acrylic foam tapes for automotive display bonding, FEA modeling has proven to be a useful tool for predicting performance in this application.

A case study is provided which describes the technique and outcome of FEA modeling for automotive display bonding with VHB Tape.

Impact Resistance

The impact resistance of a bonding adhesive is dependent on several factors including stress load direction as well as bonding joint design and the total bonding area. This investigation is based on a proprietary 3M display design using 3M VHB Tape and an FEA simulation of different impact loads that may occur during the service life of an automobile. The tape in this display design is part of the solution which may help an automotive display meet performance requirements during an impact.

To predict the material performance in FEA software, the tape needs to be characterized at the coupon level for different loads. Tests were performed including compression, tensile and shear loads at different rates and temperatures to gain an understanding of the mechanical properties of a specific 3M VHB Tape. A material data card (MDC) is the outcome of this testing. Since these tests are at the coupon level, the data was converted into automotive- display-relevant test requirements.

Compression (Front Impact)

The Headform-Impact Test (HIT) is predictive of a front impact on an automobile, which will result in a compression stress load on the tape. Different regions of the world have slightly different test requirements such as FMVSS 201 (US), or GB 11552 (PRC), or ECE R21 (EU). In these tests, an idealized human head (head diameter d=164 mm, head mass m=6.8 kg) drops onto a display with an initial speed of 20 km/h within 20 ms.

This type of test is typically done experimentally. For this study a computational finite element model of the 3M proprietary display with the main components was evaluated including the different layers beneath the cover glass. A hyper-viscoelastic material model was used to model the VHB Tape and OCA (Optical Clear Adhesives).

The plots above show the energy absorption during the impact event. Figure 3 shows an impact on the center of the screen while Figure 4 shows an impact near the corner. As shown in the plots, the highly viscoelastic 3M VHB Tape reduces the deformation during a head impact event and dampens the resulting vibrations significantly within a very short time. As the HIT is closer to the bond line, the greater the impact on the VHB Tape. In other words: the 3M VHB Tape is one key factor for high energy uptake and absorption and proved to be highly beneficial for a variety of different applications in that area.

Tensile (Rear) Impact

When considering a rear impact event, a tensile stress load is placed on the tape. During a rear impact event, high acceleration causes a significant but brief tensile stress on the tape used to secure the glass to the housing. The plots in Figure 5 below show energy absorption during a rear impact event. Acceleration used in this evaluation was 50G, which is a typical requirement by most automotive original equipment manufacturers (OEMs).

Shear Impact

For shear load two different scenarios are considered in different load directions: side impact (impact on the side of a car) or by driving over a hole (pothole) in the road. Both events will result in a vertical shear stress load on the tape. The plots in Figure 6 below show the energy absorption during a side impact event.

These figures demonstrate the viscoelasticity of 3M VHB Tape and how it provides necessary energy absorption during impact events. Figure 7 illustrates an impact-type velocity oscillation. Figure 7a details the damping difference between viscoelastic and elastic behavior. By applying oscillatory excitation, a post-pulse oscillation takes longer to absorb the oscillation on the elastic than on the viscoelastic model. For the elastic model a hyperfoam elastic model has been used.

Mismatch Compensation (Gap Filling) and Stress Relaxation

Due to manufacturing tolerances there is not always 100% alignment of substrates, or there can be uneven gaps which need to be compensated by the bond line. Typically, liquid adhesives will be used to compensate large gap differences, such as 3M Scotch-Weld Urethane Adhesive DP604NS (2 part polyurethane reactive adhesive) or 3M Scotch-Weld Flexible Acrylic Adhesive DP8610NS (flexible 2 part acrylic adhesive), especially on larger or curved displays where the gaps could be rather large.

For smaller displays, adhesive foam tapes, such as 3M VHB Tapes, are often used due to their high strength and viscoelastic behavior advantages which offer a secure bond without causing excess stress on the bond line. Most 3M VHB Tapes can compensate up to 50% of their thickness.

In Figure 8 below a perforated tape strip is used to demonstrate the stress distribution by using DIC-equipment (digital image correlation) and overlaying it with a computational finite element model. An electromechanical universal testing machine (Instron) was used in a ramp-hold test where the force was monitored over time. Stress-relaxation behavior is visible due to the viscoelastic nature of 3M VHB Tape as shown in Figure 8. The stress- relaxation behavior of the tape to compensate mismatch of substrates helps to reduce the stress on the display and avoid a visible moiré effect, which cannot be tolerated in automotive displays.

Thermal Expansion

As display sizes have increased and locations of displays are more exposed towards the windshield, this is providing significant challenges to material and component suppliers. One of these challenges is the increased temperature requirement which is causing a higher thermal expansion of the bonded substrates. What were often plastic housings used in automotive displays are now frequently changed to die-cast metal housings, such as aluminum or magnesium.

Additionally, polymethyl methacrylate (PMMA) or polycarbonate (PC) plastics were used for automotive display lenses in the past, but these are now often a glass lens. As these materials behave differently when exposed to temperature changes due to different coefficients of thermal expansion (CTEs), the bond line must compensate for the different elongations (expansion at higher temperatures and contraction at lower temperatures) of the substrates without causing any additional stress on the display components.

Figure 9 shows a thermal shock test profile where within 60 seconds there is a change from -40°C to +105°C in order to simulate a car parked during the summertime in a desert and when the car is started the air conditioning system blows cooled air towards the automotive display. As each material has its own CTE value, the elongation will happen in different rates and lengths.

This quick elongation difference needs to be allowed by the bond line and must be repeatable over the lifetime of the vehicle.

In Figure 10 the displacement of housing (magnesium) and cover glass are shown (based on an 800 mm length display). The left side shows absolute displacement of each substrate, and the right side shows relative displacement from each other. Figure 11 shows the resulting stress on each element.

3M VHB Tapes can easily withstand the elongation up to 300% of their thickness. On some tapes in this family up to 700% or more is possible depending on the strain rate. Therefore, 3M VHB Tapes can compensate the different elongations of dissimilar substrates and, through stress relaxation, reduce the stress on the display.

Vibration Resistance

3M VHB Tape is used in many applications to replace mechanical fastening methods and often must withstand dynamic stress loads. The stress loading in many applications involves cyclical type fatigue generated by the operating environment of the bonded assembly. Dynamic loading over extended periods of time can have a significant impact on the useable life span of an adhesive used for a bonding application. Therefore, when considering an application such as automotive display bonding, it’s important to have an understanding of the fatigue resistance of the tape.

As previously noted in this paper, 3M VHB Tapes are viscoelastic bonding tapes. Viscoelasticity is exhibited in the tape’s ability to both absorb and dissipate energy through its foam core. The long-term performance of the tape can be affected by extended exposure to stress and relaxation under dynamic loading conditions during the product’s life cycle in an application. An automotive display bonding application is one where the adhesive will experience cyclic fatigue throughout the service life of the electronic display due to road induced vibrations.

Test equipment exists to evaluate the cyclic fatigue resistance of an adhesive where the frequency and amplitude of the stress loading can be controlled. ISO 9664 is a test method used for characterizing the fatigue properties of structural adhesives in shear and this method, or a variation of it, can be useful for measuring the fatigue properties of acrylic foam tapes.

Stress loading conditions can be chosen based on a specific application where cyclic fatigue loading will stress a tape during its service life. An example is provided below showing an SN curve for 3M VHB Tape 5952 which shows the relationship between stress amplitude and cycles to failure at a controlled frequency of 0.4 Hz. A similar curve can be created for application specific frequencies and stress loading to gain insight into the suitability of an adhesive for an application where dynamic loading is present. Figure 12 shows 3M VHB Tape is able to withstand cyclic fatigue loading in an application where dynamic loads are present and can give insight into the long-term performance of the tape when exposed to cyclical stress loading.

Bonding and Sealing

The IP code, International Protection Marking, IEC standard 60529, classifies and rates the degree of protection provided against the intrusion of solid particles (such as dust) and liquids (water) into electrical enclosures. The rating is generically a 2-digit code, the first referring to solid particle protection and the second to liquid or water protection. Where there is no protection or where it isn’t of interest, the digit is replaced with the letter X.

It’s common in the electronics industry to use pressure sensitive adhesives (PSA) to seal devices and certify them to a particular rating: IP68 is typical. This would refer to dust tight (6 rating for solid particle) and suitable for immersion up to 1.5 meters for up to 30 minutes (8 rating for liquid). It’s important to note that this is a device level test or characterization and not something that can be tested on the PSA itself. A device manufacturer will test and rate their device, in addition to simulated devices being made to test the integrity of the PSA.

3M VHB Tapes are closed cell acrylic foam tapes and therefore they have the ability to bond and provide a waterproof seal in properly designed electronic assemblies. Die-cut shapes of tape are often used when moisture and dust resistant seals are required. A test using die cut shapes with an open center bonding two clear plastic sheets was conducted to assess the sealing capability of various 3M VHB Thin Foam Tapes while immersed in water. For this test development and characterization, IPX8 is considered equivalent to 14 psi (gauge) pressure (~10 m depth) for 30 minutes with a 1 mm line width of tape. This testing was extended to 43 psi (~30 m depth) for samples that passed the 10 m simulated depth.

Test results are provided below:

The samples used were representatives of common 3M VHB Thin Foam Tapes for electronics applications: 3M VHB Tape 86415, 3M VHB Tape 5907 and 3M VHB Tape 5980. These have passed the testing described above. These results are not to be used as a certification of device waterproofness, only to show that if used properly, 3M VHB Tapes will provide a watertight seal.

Long-term Durability of Acrylic Foam Tapes

3M VHB Tapes are inherently durable bonding adhesives due to a variety of factors including the acrylic chemistry of these tapes as well as the foam core’s ability to absorb energy and relax stress loads. The chemical bonds that make up the polymer chains consist of carbon-carbon single bonds that are highly resistant to energy in the form of heat or ultraviolet light, as well as to chemicals.

There are several ways to evaluate the durability/life expectancy of materials including cyclic fatigue testing discussed earlier in this paper. Another way to evaluate long-term performance is to conduct accelerated aging tests in high-intensity UV light chambers.

This methodology was used to study the durability of a 3M VHB Tape used for structural glazing (glass panel bonding in window and curtain wall applications on buildings) compared to the gold standard in the industry for structural glazing: structural silicone sealants. All 3M VHB Tapes are acrylic pressure sensitive adhesives and the durability of the tapes within this tape family are expected to have similar durability performance attributes, but additional testing may be appropriate for a specific tape based on the durability requirements for a specific application.

Accelerated aging was conducted at the 3M Weathering Resource Center in St. Paul, MN, with exposure up to 10,000 hours duration. The exposure used a 3M Proprietary Test Condition that has been found to be a good predictor of service durability. This 3M accelerated exposure test has proven to be a more realistic predictor of outdoor exposure results compared to ASTM G155 Cycle 1. Nominally, it provides a 2X to 3X acceleration over ASTM G155 Cycle 1. Test acceleration with accuracy is achieved by a radiant light source that very closely matches the ultraviolet component of sunlight. Note: The methodology used for the development of this test is described in R. Fischer and W. Ketola, Accelerated Weathering Test Design and Data Analysis, Chapter 17, Handbook of Polymer Degradation, 2nd Edition, S. H. Hamid, Editor, Marcel Dekker, New York (2000).

3M VHB Structural Glazing Tapes G23F and B23F (each 2.3 mm thick) were bonded between clear float glass (6.4 mm thick) and metal (black anodized aluminum) with UV exposure directly through glass. Test configuration was 1” x 1” (25.4 mm x 25.4 mm) tensile mode (ASTM D897). Samples were run in duplicate for these tests. Samples of a well-known and industry-accepted 2 part structural silicone sealant were also evaluated in this test study in the tensile mode. The geometry of these samples was the same except for the thickness of the structural silicone sealant, which was 9.5 mm. This data is provided below.

The performance of the 3M VHB Tapes was equivalent to the structural silicone sealant in this extreme accelerated aging test, which included moisture exposure and UV exposure well beyond what is required in ASTM standards for glazing sealants and demonstrates the performance of this tape for applications requiring long-term durability.

Conclusion

Automotive display bonding is a demanding application that requires high performance from the bonding adhesive due to the stress loads associated with this application.

Through the use of mechanical property and performance data, along with Finite Element Analysis simulation, a designer or engineer can consider an appropriate adhesive, such as a 3M VHB Tape, to meet the demanding requirements for their application.

Visit 3M at TTI to learn more about 3M’s Connectors (Interconnects), tools & supplies, wire & cable and more.

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Automation control systems are used for a wide range of factory automation applications in a wide mix of industries — from chemical plants to factory production lines.

Design engineers for original equipment manufacturers (OEMs) face the challenges of increasingly complex requirements in designing automation control systems that offer the functionality, reliability and safety necessary for these markets. Applications may have specific requirements for safety, performance or maintenance, for example, that engineers must factor into the design as they balance standardization versus customization and reliability versus scalable solutions.

Connectivity is one part of automation control systems that may look very simple. At its core, it is a connection between a pin and a socket. However, in any electronic system the connection point can be a weak spot where the system fails first, and a broken or malfunctioning connector could take down the entire production line. This makes reliability the most critical factor for connectors in automation control systems.

Thinking about the common challenges involved can help engineers navigate the complexities and ever-changing requirements so they can create designs that comply with the necessary specifications and produce robust and reliable systems.

Ask these questions to tackle challenges in system design

Navigating changing standards and specifications for a wide range of applications requires attention to numerous factors. These five questions can help point engineers down the right path.

1. Am I thinking upfront about connector design and specification?

Connectors are often seen as a modular and interchangeable commodity in automation control system design: one can be swapped out for another, and they will always be able to comply with necessary specifications. However, not all connectors are created equal, and there are several factors to consider when choosing a connector, including the necessary speed and power as well as any vibration or extreme temperature exposure.

Thinking about the best connector for the application at the start of the design process — rather than waiting until the end of the process to choose a connector — will help ensure that all mechanical and electrical parameters are met, and that the system will accomplish what it should. In addition, involving the connector manufacturer as early as possible means they can provide support, advice and technical expertise.

2. Do these components meet the requirements I need to deliver?

While design requirements vary by applications, in general they are becoming more complex to help ensure safer and more reliable operation in certain environments and for industry-specific end solutions. There are several complex requirements involved, including mechanical stability, electrical stability and functionality. Be aware of the capabilities of a connector portfolio. All connectors may seem similar and interchangeable until there is a problem. Selecting consumer-grade connectors that are not designed for robust industrial applications, for example, can result in performance and results that do not meet your customer’s standards or requirements.

On many devices, engineers may copy a development board or reference board that worked in a previous system and adapt it to the new system layout. However, a more holistic approach is needed to help ensure a longer-lasting product for newer automation systems.

3. Are these connectors robust enough to withstand the environment?

Every piece of hardware in automation control systems must be able to resist the worst conditions that may occur in the factory environment. The challenging conditions may include extreme temperatures, vibration, micromovements and humidity.

It is common for engineers to design one hardware solution that meets many needs and then make any necessary adjustments with software variations, it is important to optimize the hardware selection based on the most stringent safety and reliability requirements for the market and end applications. Electrical performance and stability are key, but do not forget to consider mechanical stability as well.

4. Is a smaller system more vulnerable?

Looking holistically at a system’s design early in the process often results in the use of smaller components and parts; intelligence can be moved to the edge and more computing power can be planned for a smaller space. Starting with something smaller can make the product more competitive; however, it is important to think about the increased risks with much smaller products. They could be more vulnerable to breaking, electrical noise interference or mechanical instability, so it is key to find a compromise between miniaturization and mechanical stability.

You must optimize the combination of data speed, reliability and miniaturization to make sure all mechanical stability and electrical performance requirements are met. The smaller your product becomes, the more critical the assembly and production of the product is, as well as the design and construction of the components inside the system. The mechanical tolerances in the system should be designed to help prevent generating frictions or loads that could jeopardize the connection over time.

5. What is the total applied cost of this solution?

Taking a holistic approach in system design helps deliver a total applied cost that is more competitive. It goes beyond looking only at component cost. Total applied cost also considers the design, manufacturing process, system life and any ongoing maintenance. Using well-designed, reliable components ultimately results in minimal quality problems and returns — for a lower total applied cost. Avoid the short-sighted approach of choosing the cheapest components based solely on the cheapest cost without considering other factors such as long-term maintenance or quality costs.

Evolving trends in automation control systems

Several trends are shaping the future of automation control systems and customer expectations. Paying attention to these evolving technologies and areas of interest can help design engineers stay ahead of the curve in producing more reliable, adaptable systems. Here are four trends to be aware of:

Miniaturization: The demand for miniaturization is affecting electronic components in many industries. As parts and machines used in industrial factories become smaller, the controllers and components inside those solutions must become smaller as well. But while the size is reduced, speed and power requirements remain the same — or are increasing. All of the environmental issues, such as vibration or temperature requirements, also remain the same. With miniaturization, choosing the right industrial connector solution becomes very important to get the durability and reliability needed from the component. The impact of a bad decision regarding components is amplified as the solutions become smaller.

Increasing power requirements: The processing power available in these components and systems continues to grow to new levels. One factor driving the adoption of new systems is the ability to extract information from the field and put it seamlessly into the hands of decision-makers — at their desks or on their laptops or tablets. Industrial connectors must be reliable and allow for greater bandwidth to take advantage of these advancements in power and capabilities. Think of the connector as a pipe. If there is a broken pipe, the water cannot flow.

Impact of artificial intelligence (AI): This technology could have a significant influence on design cycles and how automation control systems are designed. For example, if a manufacturer has very specific system requirements, these could be loaded into the solution using AI. The increasing processing power (as mentioned above) in these systems can allow engineers to make meaningful strides using AI. The implications for connectivity are all about more bandwidth and speed and continuing to increase those capabilities in harsh environments.

Sustainability and energy efficiency: How will a push for sustainability impact a customer’s selection of components? Sustainability requirements influence the specifications and what customers expect in terms of products and solutions. The push for more sustainability and energy efficiency in automation control systems is in the early stages, but customers will expect more from OEMs on this front in the coming years. It is important to consider such questions as how are we handling wastewater? Are products fully recyclable? Making these issues a key part of system design is not far down the road.

How can TE Connectivity help design engineers be more nimble?

TE Connectivity (TE) has an expansive portfolio of reliable connectors designed to meet a wide variety of automation control system needs for factory and manufacturing applications. TE can help OEM design engineers navigate the ever-changing standards for these systems and their components, acting as a trusted partner in producing flexible and durable systems that deliver value.

Our engineers are connector experts skilled in helping you address connectivity requirements. They bring product and application expertise and engineering know-how so you can build your product offering with an application lens. For OEMs dealing with a shortage of skilled labor in-house, TE can help fill this expertise gap. Bringing in TE experts early in the process can help ensure that the solution is optimized to meet application requirements and needs.

In addition, TE’s rugged and durable connector solutions will provide long-term performance and value, and the portfolio meets a broad range of application needs. For example, if the application standards require components that can endure high vibration or corrosive elements, TE has connectors specifically designed for optimized performance in these conditions.

Connect With Us

You do not have to navigate the challenges and complex requirements of automation control system components alone. Partner with TE to find the right connector solutions for your customers’ applications so you can deliver systems that provide reliability, functionality, safety and optimized performance. Connect with us today.

About the Authors

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Electric vertical takeoff and landing vehicles, or eVTOLs, can fly like common commercial drones, taking off and landing without requiring long airstrips. While drones typically have blades affixed to motors pointing directly upward, more modern eVTOLs can take advantage of movable engines that allow for more forward thrust, thereby improving efficiency. Cables and connectors play a surprisingly important role in the viability of eVTOLs and their impact on overall mass. Knowing how the right connectors and cables will aid in design can help engineers create viable and sustainable eVTOLs.

Compared to helicopters, which are notoriously difficult to pilot, such vehicles are far easier to manage due to simplified controls. Additionally, the vast amount of software and hardware already developed to create autonomous drones means that eVTOLs are ripe for deploying autonomous flight systems, thus eliminating pilot error.

Most airspace above urban zones is virtually unused, so eVTOLs could move around at high speed, significantly reducing transportation times between locations. Thus, eVTOLs could ferry people and cargo within urban environments, reducing road dependency and making highways more ideal for transporting heavy goods.

Bridges and tunnels can increase road and rail traffic capacity, but the massive infrastructure cost makes such projects hard to justify. eVTOLs would merely need landing pads and charging stations. This not only reduces costs for taxpayers but also lowers maintenance expenses, as roads will experience less traffic if pedestrians use eVTOLs.

While they offer many benefits, eVTOLs face many design challenges if they are to become an effective mode of transportation. In this article, we’ll discuss these challenges while focusing on the interconnect design and its importance in the development of efficient and effective eVTOLs.

What challenges do eVTOLs face?

Despite all the advantages that eVTOLs present, they are still more of a concept than an actual solution that can be deployed in a commercial environment, and this reality comes down to numerous challenges that they face.

The first, and arguably the most critical factor, is weight. Because eVTOLs are entirely electric, they must carry hefty batteries. Compared to fossil fuels, batteries have far less energy density, meaning that any battery is far heavier than a tank of gasoline with the same energy capacity. For comparison, the energy density of gasoline is 47.5MJ/kg compared to lithium-ion batteries at 0.3MJ/kg.

Due to the need for heavy batteries, the rest of an eVTOL needs to be as light as possible. While modern materials such as carbon fiber can achieve this, they come at an added price and design complexity.

If eVTOLs become autonomous, communication between each eVTOL will be essential due to the severity of possible collisions. eVTOLs will need to be able to see the flight path of all other vehicles and plot a safe route accordingly. Such a network would need to handle vast amounts of data in real time with significantly reduced latency. According to researchers at KAUST, latencies down to 10 ms will be needed for autonomous flight control.

At a minimum, an eVTOL network would need to work on top of a 5G network, utilizing edge computing to have data immediately routed to other vehicles (i.e., not pass through ISPs). However, integrating cellular communication systems and onboard artificial intelligence for autonomous flight introduces additional systems and components, further increasing weight and reducing the energy available to the craft for flight. Energy efficiency is of paramount importance, and designers must reduce the weight of any and every component. Depending on the size of the craft, electronics can account for 20% or more of the total weight.

How do connectors and cables come into the picture?

Cables and connectors may not seem as critical as other components in the design of eVTOLs, but their importance is quickly realized when exploring each aspect.

Connecting and powering the various eVTOL systems requires long cabling lengths, sometimes adding up to miles, which can account for a significant portion of the aircraft’s total weight. Power cables alone can account for close to 1% of the total weight of a 5,000-lb. craft. The signal and data cables further increase this number. Power cable weight is seen as such a significant weight contributor that aerospace engineers at NASA have studied how the design of power cables can be optimized to minimize weight.

Since eVTOLs are entirely based on electricity, electrical stress can be extremely high, with high voltages and currents present. This means that any cable and connector used to deliver power from the batteries to the motors needs to handle such power levels safely and have sufficient insulation to provide adequate protection, which tends to lead to large, bulky cables. Ensuring the optimal conductor and insulation materials can help limit power cables’ impact on overall weight. Many engineers designing eVTOLs opt for solutions commonly found in aviation platforms, including aluminum cables that are designed with these concerns in mind.

Whether high voltage or current is chosen, the final cable and connector choice must reduce weight as much as possible. Any extra weight in an eVTOL will increase the difficulty of takeoff and limit its range.

Such connectors must operate safely in extended temperature ranges while retaining a high IP rating to prevent damage during poor weather conditions. Consider, for example, the connectors found in the landing gear, rotary motors, antenna systems for GPS and radar for eVTOLS. Most of these systems have some or much exposure to the environment. When landing in cities such as Dubai these connections may face weather conditions that include sandstorms, extreme temperature changes, sudden torrential rain, and high winds.

Finally, as all these connectors and cables are being used in an environment subjected to shock and vibration generated by motors and landing/takeoff, any connector used must resist accidental disconnects over extended use. As such, simple screw terminals or clips will likely be insufficient, requiring locking nuts, press-fit connections and unique mating mechanisms.

How can RF connectors help power the future of eVTOLs?

A wide range of compact RF connector styles and mounting options is available to satisfy the various RF needs of an EVTOL. This includes connectors down to 1.0 mm, which can operate at frequencies up to 110GHz. This makes them ideal for all aviation tracking systems, including ADS-B and Pilot Aware. They can also be used with cellular systems, including 4G, 5G, and mmWave bands of 5G.

For designs that require communication speeds beyond copper’s capabilities, a range of optical connectors can help engineers achieve extremely high inter-device speeds across the entire eVTOL and do so at significantly reduced weight due to the use of tiny fiber-option cables. Such cables are also immune to electromagnetic interference, making them far safer for use in autonomous environments where sensor data cannot be compromised.

Not all connectors can be replaced with RF or fiber optics. For such applications, micro-D connectors become invaluable. Their design allows for either shielded or unshielded cables to be used. In cases where EMI is not a concern, the absence of shielding can help reduce size, weight, and cost. Their specific D shape also makes them polarized. Compared to standard D-sub connectors, micro-D connectors are significantly lighter and take up to 80% less space while offering the same performance in the harshest environments.

Conclusion

While there is a lot of hype surrounding eVTOLs, they are still in their infancy, and any existing systems are more of a concept than an actual viable design that could be supported economically. The extreme technical challenges faced by eVTOLs and endless amounts of legislation present numerous roadblocks to engineers when trying to get such ideas to take off. However, the industry has growing confidence that the necessary infrastructure can be built and that technological roadblocks, such as battery density, will be overcome.

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Recently, due to emerging high frequency and wide band gap switches like GaN and SiC, miniaturizing the converter is one of the most important criteria for power electronics engineers. In power electronic converters, magnetic components, like high power inductors, are the key components and correctly designing them has considerable effect on the net efficiency and size of the power converter.

Among high power inductors, there are a wide range of applications where the inductor current has high frequency and very low frequency, or DC components like DC-DC inductors, power factor correction (PFC) inductors, output filter inductors and chokes. In such applications, designing the winding and selecting the wire type is the most challenging part of the design, to comprise and control both low frequency and high frequency conduction losses.

To solve the problem, one solution is using litz wire, however, it has poor porosity or filling-factor of about 40 – 50% for high frequency applications. Hence, compared to solid copper wire, litz wire makes the power inductors bulky with higher direct current resistance (DCR), which adversely affects the power losses for low frequency or DC currents. Due to this fact, in recent power converter applications, new inductor winding structures are proposed based on solid wire and companies like Bourns are manufacturing flat wire inductors for renewable energy applications. However, improper designing of solid wire increases ESR for high frequency applications.

To make an optimal compromise between DCR and ESR at high frequencies, several solutions based on solid copper wire have been proposed in the literature. For example, in, a design procedure for round wire is presented with a single layer winding structure to reduce ESR for high frequencies. However, this winding structure is suitable for toroid shapes, while for the other core geometries such as a P-core geometry, the inductor will become bulky and a major part of the core’s window area remains empty. Another alternative is multi-layer foil windings; however, this wire type is suitable for medium frequency transformers with interleaved windings. For inductors and other multi-layer windings, foil wire presents higher losses due to the proximity effect between the layers.

Among different solid wire types, flat spiral and helix shapes present superior performance, while they have better manufacturability in printed circuit boards (PCBs) and a reduced size of magnetic components. Spiral shapes have proximity effect issues and are more suitable for high frequency planar transformers. Solid flat wire winding presents better thermal conductivity and DCR; however, more work is needed to have accurate and simple models suitable for design optimization algorithms. Fig. 1 shows a power inductor based on a helical flat wire coil.

This study accurately models and formulates inductor DCR and ESR based on solid flat wire. Then, the performance of this structure is compared to solid round wire with equivalent wire gauge and window size, using 2D FEM simulations. In this research, the formulation and simulations are considered for inductors with cylindrical geometries such as PQ and P-core types, which are considered the most frequently used core geometries with higher power density and fewer leakage flux problems.

The main parameters of the solid flat wire inductor are defined based on equivalent winding parameters with multi-filar solid round wire. Then, the solid flat wire formulations for DCR and ESR are derived. Next, 2D FEM simulations are presented and the two winding structures are compared. Based on FEM simulations, the ESR formula is further modified, and conduction losses of the inductor are formulated for DC-DC converters. Finally, experimental results for a laboratory sample with flat wire are presented.

Modeling of the Flat Wire Inductor

Without loss of generality, the main parameters of the flat wire coil are formulated based on an equivalent inductor with solid round wire, which has a similar winding area, i.e., equal winding internal radius, r_w, radial thickness, D_w and height, H_w, as shown in Fig. 2. Furthermore, it is assumed that round solid wire has a non-twisted bundle containing m strands, or m-filar, with diameter of d_s. In this paper, it is assumed that solid round wire has few non-twisted strands. Obviously, a higher number of twisted strands improves ESR, however, in this case the wire is classified as litz wire and not solid wire.

Regarding Fig. 2 and the round wire parameters, the flat wire thickness, t_w, can be calculated by:

Assuming a unit porosity factor for the round wire inductor, i.e., negligible space between round wires, the filling-factor of copper cross section area would be equal to π/4. Then, assuming a similar copper filling-factor for the flat wire winding, the space between turns, s, is derived by:

Considering the cylindrical symmetry shown in Fig. 2, the conductance of a differential ring, dG, with a distance of r from the z-axis and differential cross section area of t_wdr is:

Here, σ = 5.8 × 10⁷ S/m is the conductivity of copper. Each turn can be considered as an equipotential surface and the total conductance of one turn, G, can be derived by:

Using (4), the DCR of the flat wire winding, R_dc, with N number of turns, is derived from:

It is worth noting that the helical effect on the length of the winding is neglected in (5), since the pitch of the coil is much lower than the coil’s mean diameter, i.e. (t_w+s) << (2 r_w+D_w).

To calculate ESR, R_ac, under sinusoidal alternating currents (AC), several analytical solutions have been developed in literature. However, they are mainly developed for solid round wire. For rectangular conductors, recent analytical formulations are developed only for a single solid flat wire in 2D x-y plane. Furthermore, according to the analytical solutions, the formulas are accurate when the thickness of the conductor is less than double the skin depth, δ, which is defined by (6).

Here, μ0 and f are the vacuum permeability and frequency of the sinusoidal current, respectively. For high power inductors, the flat wire thickness, t_w, is typically selected high enough to carry high currents and for high frequency DC-DC converters, typically t_w ≥ 2δ. Hence, in this study, analytical formulations will not be accurate enough.

Neglecting the fringing effects of the distributed air gaps, shown in Fig. 2(b), to calculate R_ac, first it is assumed that the inductor current effectively passes through rings with radius of r_w and thickness of skin depth,δ, by assuming t_w << D_w. Hence, the ESR, R_ac, as a function of f, is calculated in (7), by assuming that δ is much smaller than D_w and t_w ≥ δ.

However, rings-model is affected by edge-effects of the first and last turns and the space between turns, s. Using FEM simulations, it is shown that for a specific N and t_w, this model can be corrected by a fix correction factor of k_w, as included in (7) and the presented formulation accurately derives R_ac in a wide range of operating frequencies defined by:

Here, f_min is the minimum frequency at which the model is accurate and is defined by t_w ≥ δ criterion using (6). Next, FEM simulations are presented to compare the two different solid wires and Rac model assumed in (7).

2D FEM Simulations and Modified ESR Formula

To calculate Rac, 2D Poisson equation for the magnetic potential, A, under steady-state condition, is solved in (9), neglecting the displacement currents:

Where, J_s, J_ind and J_t are the peak density values of source current, induced current and total current, respectively. For operating frequency of f, J_ind relates to A, as presented in (10), and the relation between the inductor’s peak current, I_L, and J_s are obtained by (11), as follows:

In (11), the integral is calculated on a surface area of one turn. By solving A, R_ac can be achieved by calculating ohmic loss in all cylindrical coordinate and dividing the calculated loss by the squared value of the inductor current, as follows:

To compare the two solid copper wires, first it is assumed that the power inductor is implemented with solid round wire with N = 8, r_w = 12.5 mm, and m = 4 with d_s = 1.50 mm. In this design, 20 μm is considered as the insulator thickness between conductors, which has negligible effect on the final dimensions and DCR.

Hence, D_w and H_w are calculated at approximately 6 and 12 mm, respectively. On the other side, according to Fig. 2 and using (1) and (2), t_w and s are calculated at 1.178 and 0.322 mm, respectively. The two inductors are implemented by a PQ50 core with a height of 33.0 mm. For the sake of simplicity, in the following simulations, the core is considered linear and lossless with a relative permeability, μr, of 2400. To have a negligible fringing effect, three 0.25 mm gaps are considered at the center leg of the core.

To calculate the DCR of the two inductors, two FEM magnetostatic simulations have been done for the two inductors. The DCR for the flat wire and round wire inductors are derived as 1.8766 and 1.9590 mΩ, respectively, meaning that the inductor with solid flat wire has a 4.2% lower DCR. On the other side and using (5), the DCR is calculated at 1.8770 mΩ, which is very close to the magnetostatic simulation result, at approximately a 0.02% margin of error.

Fig. 3 shows a 2D Eddy-current FEM simulation and the mesh plot for the solid flat wire inductor model with f = 100 kHz and an AC peak current of I_L = 5 A. Based on 2D eddy-current FEM simulations, the inductor value is calculated at approximately 34.8 μH. By using (12) and post-processing the magnetic vector potential, A, R_ac is derived at approximately 33.3 mΩ. As seen in Fig. 3(b), except for the edge effects, the current mainly passes through rings.

Using similar FEM simulations, ESR for the solid round wire inductor is calculated at 49.0 mΩ, i.e., 47.1% higher than the flat wire inductor. For the round wire design, there are two main reasons behind its higher ESR. The first reason is that the coil has two layers and the number of layers adversely affects the winding’s ESR. The second reason is the fact that here the bundle is not twisted, and the current is not uniformly distributed between the four strands.

Fig. 4 compares the ESR of the two designs for different frequencies up to 1 MHz and shows that the solid flat wire is significantly better, especially at higher frequencies, while the proximity effect between the two layers of the round wire design increases significantly. It is worth noting that for solid wire design with fewer parallel branches, m < 4, the ESR will be even higher which confirms the superiority of solid flat wire.

To show the proposed assumptions described in (7), FEM simulations under different operating frequencies are done for two inductors manufactured with solid flat wires. Table 1 presents the calculated R_ac for the two inductors with N = 4 and 8, and similar t_w = 1.178 mm and s = 0.322 mm. Using (8), f_min is calculated at approximately 3 kHz, hence Table 1 presents the results for frequencies from 3 kHz up to 1 MHz. To calculate k_w, first, R_ac is calculated by (12) using FEM simulations. Then, using (7), the physical parameters of the winding and the known Rac, kw can be calculated for each FEM simulation, as included in Table 1.

According to Table 1, kw for the two designs is almost constant with less than a 4.2% variation from 3 kHz up to 1 MHz. Similar FEM simulations have been done for D_w = 9.0 mm and f = 100 kHz, and k_w values for N = 4 and 8 are derived at approximately 0.4768 and 0.7510, respectively which are very close to the results presented in Table 1. This means that for t_w << D_w, which typically occurs for high power inductors, k_w is approximately independent of D_w. Hence, assuming the constant filling-factor of π/4 defined in (2), k_w only depends on the number of turns and wire thickness. Typically, inductors based on flat wire are made with few turns, and it is feasible to calculate a table-function of k_w (N, t_w) for calculating ESR in a wide range of operating frequencies, which is suitable for design optimization algorithms.

As concluded from the above-mentioned analysis and simulations, equation (7) can model R_ac in a wide range of operating frequencies. Hence, it is possible to formulate the conduction losses of flat wire inductors for DC-DC converters as follows. As an example, for a buck converter with a regulated output voltage of VO and load current of IO, the maximum current ripple occurs at a duty cycle of 50%.

In this condition, the voltage of the inductor, L, is like a square wave voltage source with an amplitude of V_O and switching frequency of f_s. Using the Fourier series, the inductor voltage, v_L(t), and its hth current harmonic amplitude, I_h, can be formulated by:

Hence, using (7) and (14), the maximum AC conduction losses, P_ac, are derived by:

Here R_ac^h calculates the ESR for hth harmonics, i.e., for f = hf_s, by using (7). In (14), the current amplitude significantly reduces for high order harmonics, hence, the AC conduction losses can be well approximated up to the 9th harmonic, as follows:

Moreover, it is assumed that the self-resonant frequency of the inductor is higher than the 9th harmonic and the inductance value of L can be considered constant in the above-mentioned analysis. DC conduction loss, P_dc, is calculated by (17), where R_dc is the DCR of the inductor calculated by (5):

Finally, a simulation has been done for a buck converter with f_s = 100 kHz, V_O = 100 V and I_O = 30 A based on the flat wire inductor the number of turns = 8 and L ≈ 34.8 μH, as presented in Table 1. It is assumed that the output voltage has negligible ripple, and the duty cycle of the buck converter is 50%. Using (16) and (17), P_ac and P_dc are calculated at approximately 0.558 W and 1.689 W, respectively. The calculated values have been verified by doing a transient FEM simulation with a time step of 50 ns. According to the FEM results, the total conduction loss, P_ac plus P_dc, are calculated at approximately 2.402 W which has at approximately 5.5% deviation from analytical calculations.

Experimental Results

To verify the analytical formulations, a 5.6 μH, 80 A power inductor is implemented with N = 4, t_w = 2.0 mm, D_w = 9.5 mm, s ≈ 0.6 mm and r_w = 11.0 mm, as shown in Fig. 5(a).

To have 5.6 μH inductance, three 0.4 mm air gaps are required at the middle leg of the core, to reduce the fringing effects. However, for the sake of simplicity, only one 0.4 mm gap is considered for ESR measurements. The core is PQ50 with N95 ferrite material and a height of 33 mm. According to (5), DCR is calculated at approximately 387 μΩ for this inductor, including 4.5 cm extra length of wire for the end terminals. To measure DCR of the inductor, a 25 A DC current was applied to the inductor and voltage of approximately 10.0 mV was measured at room temperature, which means that the DCR is measured at approximately 400 μΩ, i.e., a 3.35% margin of error from theoretical calculations.

For this inductor and using FEM simulations, the correction factor, k_w, for the mentioned N and t_w is calculated at approximately 0.9764, with less than 4.0% deviation from f_min ≈ 1 kHz, defined by (8), up to 1.0 MHz. To measure the ESR, it is worth noting that the core also reflects extra ESR in the inductor coil, due to the eddy-current and hysteresis losses in the core.

To exclude the reflected resistance from the core, the ESR of an inductor made by 1050×0.05 mm litz wire, N = 4 and the same core is measured as the reference measurement. Regarding FEM simulations, AC and DC resistances of the litz wire are very close to each other for operating frequencies under 100 kHz, with less than a 2% change. Hence the measured ESR of the reference inductor with the litz wire is approximately equal to its DCR plus the extra ESR reflected from the core. Using a WYNE KERR 6500B impedance analyzer and f = 100 kHz, the total ESR, including the core effects, for the flat wire inductor and the reference inductor with litz wire are measured about 14.6 and 6.4 mΩ, respectively. Moreover, the DCR of the reference inductor is measured at approximately 4.2 mΩ. Hence, the ESR of the flat wire winding at 100 kHz is measured at approximately 12.4 mΩ, which has about a 12 % error from (7) with the mentioned kw.

Conclusion

This article presents modeling and analysis for high power inductors manufactured with solid flat wire and develops formulations to accurately calculate their AC and DC resistances. The simulations and experimental results show that the flat wire type presents superior DCR and ESR, compared to a non-twisted solid round wire, using an equivalent wire gauge and window area. Furthermore, by using FEM simulations, a correction factor has been defined to accurately calculate ESR for different turn numbers and wire thicknesses, with less than a 5% error, which is suitable for design algorithms. The model has been verified by experimental results and further FEM simulations using different wire sizes and number of turns in a wide range of operating frequencies. Furthermore, based on the ESR formula, the maximum AC conduction loss of a flat wire inductor has been formulated for buck converters.

To learn more, visit TTI Inc.

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The growth and evolution of photodetectors started with military investments and defense needs. During the Cold War, significant advancements in low-light detection technologies were driven by military needs, particularly for heightened surveillance and communication systems. Technologies such as the avalanche photodiode (APD), first patented by Jun-ichi Nishizawa in 1952, were heavily researched in the 1960s and 1970s and were pivotal in advancing photodetector capabilities. Post-Cold War, these technologies transitioned into civilian applications, leading to widespread industrial and consumer adoption.

Best practices for innovating with photodetector technologies

The types of photodetectors vary based on the material used, the operational mechanism, and their application-specific properties. These devices range from basic PN junction photodiodes to advanced technologies like avalanche photodiodes (APDs) and quantum dot photodetectors. Other types include photomultiplier tubes (PMTs), charge-coupled devices (CCDs), metal-semiconductor-metal (MSM) photodetectors, and emerging materials like graphene-based photodetectors. Each type has distinct characteristics, making them suitable for a variety of applications, including telecommunications, autonomous systems, medical imaging, environmental monitoring, industrial scanners and consumer electronics. It’s imperative to begin any design and engineering process by understanding what the application needs and asking all the questions upfront during the planning stage.

Some key considerations are:

• Spectral range and materials: Spectral range is the range of wavelengths over which the photodetector is sensitive, typically measured in nanometers (nm). The below image shows some of the photodetector materials that are used to detect signals ranging from UV wavelengths to Long Wave Infrared (LWIR) wavelengths. With the longstanding evolution of photodetector technologies, many materials for components currently in use may be outdated compared to new advancements. Development of compounds like Silicon carbide (SiC), Gallium nitride (GaN), indium gallium arsenide (InGaAs), and other semiconductor materials like InGaAsSb have enhanced photodetectors’ sensitivity and spectral range. These materials detect short-wave infrared (SWIR) and middle-wave infrared (MWIR), increasing their versatility. Organic, graphene-based and flexible photodetectors expand possibilities for wearable technology and biomedical applications.

• Quantum efficiency (QE): Quantum efficiency is the ratio of the number of charge carriers generated to the number of incident photons, often expressed as a percentage.
• Detectivity (D*): Detectivity is a normalized measure of a photodetector’s sensitivity, expressed in Jones (cm·Hz^1/2/W). It combines responsivity and noise characteristics. Responsivity measures the electrical output per unit of optical input power, typically expressed in amperes per watt (A/W) or volts per watt (V/W).
• Noise: A constant consideration with sensitive components is its bulk noise, which is a combination of the shot and Johnson noise of the detector and often is derived from the dark current of the detector. Noise equivalent power (NEP) is the amount of optical power required to generate a signal equal to the noise level of the photodetector, typically measured in watts per root hertz (W/√Hz).
• Device architecture: A photodetector’s architecture, including the active area, the device thickness, and the composition of each layer impacts its efficiency, capacitance and response time. Advanced designs that incorporate specialized epitaxial layering, such as heterostructures and quantum wells, can enhance performance. Pixel configuration for imaging applications is critical. Higher pixel density can improve resolution, while larger pixels may enhance sensitivity.
• Speed and response time: Response time is the time it takes for a photodetector to respond to an optical signal, typically measured in nanoseconds (ns) or picoseconds (ps). This impacts the detectivity of photodetectors. Innovations in materials with high electron mobility have lowered capacitance, increasing the bandwidth (Hz) of photodetectors.
• Integration: Close collaboration with end-users and industry partners helps to develop photodetectors that meet the precise needs of various applications. Hybrid integration of photodetectors with other components, like receiver systems, leads to more efficient and scalable solutions, improving performance while broadening their application scope.
• Reliability, durability and robustness: Developing photodetectors that can withstand extreme conditions, such as extreme temperatures, mechanical stress and radiation, has expanded their use in military, aerospace and industrial applications. This goes hand in hand with thermal management and packaging. Advances in coatings and packaging techniques have demonstrated improved photodetector reliability.
• Costs and resource: Costs and resources naturally impact all decision-making and capabilities for investing in growing photodetector technologies. Photonic integrated circuits allow for compact, high-performance systems that are cost-effective. Advances in nanofabrication have allowed for the creation of smaller, more efficient photodetectors. Developing photodetectors compatible with other high-volume semiconductor manufacturing process technologies like complementary metal-oxide-semiconductor (CMOS) facilitates the production of affordable, high-performance sensors.  

Photodetector engineers can balance heightened specialization with optimized approaches for success, scalability and future growth by having these conversations on the front end. It’s important to balance overall best practices with the application’s specific standards and certifications, especially for consumer, automotive, aerospace, defense and medical industries.

Photodetector technology supplements and revolutionizes many applications

Today, photodetector technology is a vital component that underpins countless technologies, including gas sensing, motion sensors and consumer electronics. In telecommunications, it enables high-speed data transmission in fiber optic networks. In aerospace and defense, they’re used for target recognition and range finding; in R&D, there’s a wide range of spectroscopy applications. Their 3D scanning applications are essential in architecture, construction, autonomous vehicles and industrial controls. Photodetectors also enable environmental monitoring to detect pollutants and monitor environmental changes.  Photodetectors are also pivotal in medical imaging and are used in devices like CT scanners and MRI machines for precise imaging and remote patient monitoring technologies.

Photodetector evolution comes with growth challenges

Acknowledging common industry pain points from the beginning positions engineers and organizations with the information they need to address and mitigate challenges. The photonics industry is small, requiring talent to collaborate frequently within and across disciplines. Having dedicated foundries for photodetectors may not be financially viable. As a result, partnership is vital for meeting the technical demands of development. Universities and research entities stand at the forefront of evolution.

Systems integration presents another challenge, given unique applications and the need for collaboration within photonics technologies. This demands a clear understanding of the product, environment and objectives which is especially critical for custom, application-specific developments.

Optimizing size, weight, power and cost (SWaP-C) is a paramount concern for the design and development of photodetector technology. Investments and specially dedicated resources are essential to future-proof designs for growth and innovation while offering a competitive edge for organizations in nearly every industry.

The future of photodetector technology is bright

Growth and innovation in applying photodetector technology will undoubtedly continue over time. As this technology becomes more widespread, its success is showcased by how little individuals notice the impact on their everyday lives. The seamless integration of photodetectors into various applications is a testament to their efficiency and effectiveness. Knowing what to expect is essential to harnessing the benefits and opportunities of this next wave of innovation. Advancements in materials, quantum photonics, AI integration and sustainable technologies promise to enhance performance, efficiency and cost-effectiveness, driving innovation in autonomous systems, security, medical diagnostics, environmental monitoring, consumer electronics and beyond. As organizations continue to develop and integrate these technologies, there’s no denying the widespread potential for photodetectors to address complex global challenges and improve everyday life. The future holds exciting possibilities, with these advancements seamlessly blending into the fabric of our daily experiences.

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Recent growth in renewable energy generation has triggered a corresponding demand for battery energy storage systems (BESSs). The energy storage industry is poised to expand dramatically, with the G7 recently setting a 1500GW global energy storage target for 2030. Meanwhile, BloombergNF estimates that investments in energy storage will grow to $103 billion over that period. At the same time, the cost per kilowatt-hour of utility-scale battery systems is likely to drop significantly, making controlling system costs critical.

Battery systems aren’t just designed to serve as local power backups, such as the systems used to power critical facilities (including hospitals and data centers) when the normal power source fails. BESSs also offer other benefits and ancillary services, including load-leveling, spinning and regulation reserves, frequency regulation, transmission and distribution deferral. These features maximize BESSs as a valued asset to utilities.

Today’s BESSs are increasingly designed to feed local micro-grids to supply power to small areas when demand rises. They store electrical energy produced by solar or wind power generators, then inject that energy back into the grid when needed.

As the power density of modern lithium-ion batteries grows, BESS integrators are striving to offer their customers more power in a smaller footprint. However, with higher power levels, circuit protection becomes increasingly important.

BESS circuit protection

Renewable energy providers are incorporating new generations of high-efficiency power semiconductor devices into their systems to control power in inverters and converters. Because these are sensitive electronic devices, they require robust protection against energy surges. The design of BESSs can still be considered to be in its infancy, given that the technologies that go into them are evolving rapidly. As a result, many of the electrical engineers integrating those solutions are seeking guidance in selecting and implementing appropriate circuit protection strategies.

A comprehensive circuit protection strategy is crucial to meeting BESS integrators’ most critical objectives:

• To prevent costly service interruptions to end-users with critical uptime requirements, such as hospitals, industrial processing plants and data centers. For example, the cost of data center downtime is in the range of $8,000 per minute.
• To prevent revenue losses for renewable energy suppliers.
• To prevent power disruptions to the local area.
• To protect the workers who will install and maintain the BESSs that integrators design.
• To prevent damage to the BESS equipment itself, which would jeopardize the sizable investment that the end-users or renewable energy suppliers have made.
• To provide grid stability via power generation from renewable sources.

Electrical faults within a BESS can pose significant hazards to workers, including the risk of electric shocks, chemical/electrolyte burns, and the release of toxic or explosive gas. The three main areas of concern are protection against electrical overcurrents, ground faults and arc-flash hazards.

Overcurrent protection

Inverter protection is one of the most important facets of BESS circuit protection. Inverters are typically — although not always — located outside of the trailer or other enclosure in which the banks of batteries are housed. A DC/AC inverter converts direct current (DC) output from batteries into a utility frequency alternating current (AC) that can be fed into a commercial electrical grid. However, a BESS also allows storing the DC current generated by renewable energy sources to a bank of batteries. Later, when there’s a demand for that stored power, a DC/AC inverter converts the DC battery power into AC power that can then be exported to the grid.

In order to provide the longest possible battery discharge times, BESS designers are building in large battery banks. Each of those batteries represents an energy source. Any fault in the system can lead to dumping a massive amount of energy all at once — with all the dangers to people and equipment that could pose.

In the 2017 edition of the National Electrical Code (NEC) Article 706 spells out the overcurrent protection requirements for Battery Energy Storage Systems. The code says:

• Disconnecting Means: “A disconnecting means shall be provided at the energy storage system end of the circuit. Fuse disconnecting means or circuit breaker shall be permitted to be used.”
• Direct Current (DC) Rating: “Overcurrent protective devices, either fuse or circuit breakers, used in any DC portion of an ESS shall be listed and for DC and shall have the appropriate voltage, current, and interrupting ratings for the application.” Exception: Where current-limiting overcurrent protection is provided for the DC output circuits of a listed ESS, additional current-limiting overcurrent device shall not be required.
• Location: “Where energy storage system input and output terminals are more than 1.5m (5 ft) from connected equipment, or where the circuits from these terminals pass through a wall or partition, overcurrent protection shall be provided at the ESS.”
• Sizing: “Overcurrent Device Ampere Rating… provided on systems serving the ESS and shall be not less than 125 percent of the maximum current calculated.”

The existence of these Code requirements helps validate the importance of selecting the proper overcurrent protection in the ever-growing market of BESSs.

A wide range of fuses are available to handle a variety of current overload applications. High-speed fuses are the usual choice for these DC ESS applications because they are much smaller, faster and less expensive than DC circuit breakers. The maximum interrupting rating for circuit breakers tops out at about 200,000 to 300,000 amps. In contrast, the latest generation of high-speed fuses (such as Littelfuse PSR Series High-Speed Square-Body Fuses) (Figure 1) can interrupt up to 150 kA of DC current (or 200 kA AC) in a much smaller footprint than a DC circuit breaker.

High-speed fuses are designed to operate about 24 times faster than conventional fuses in order to protect sensitive power semiconductor devices (such as diodes, triacs, IGBTs, SCRs, MOSFETs and other solid-state devices) that are built into inverters, UPSs, battery management devices and other systems, by reducing peak let-through current and let-through energy (I²t).

These fuses are also invaluable for protecting a BESS’s DC batteries. Each battery is protected by DC fuses at the positive and negative terminals to isolate the battery during any internal short-circuit condition. DC combiners, where the outputs from multiple battery racks are combined to feed the inverter, are critical locations that are susceptible to high DC overcurrent faults. Typically, at this location, output strings from batteries are protected by DC fuses with the highest possible DC interrupting rating.

Ground faults

A variety of factors can contribute to the development of ground faults. These factors include insulation or component degradation (often as a result of overvoltage or overtemperature), humidity/moisture, rodents, dust accumulation between live parts of the system and human error. Unless an appropriate ground-fault device is used, low-current ground faults can often go unrecognized.

BESSs are typically ungrounded systems. The system may remain in operation after the first ground fault, resulting in higher voltage on the unfaulted bus, with reference to ground, but with no current flow. However, subsequent ground fault on the opposite bus can have catastrophic consequences from both an equipment-protection and worker-safety perspective. A second ground fault on an ungrounded system may constitute a phase-to-phase fault that can result in arcing, fires and severe damage or injuries. Most electrical faults, including arc flashes, begin as ground faults and so detecting these faults early is essential so they can be addressed before serious damage or injury occurs.

For ungrounded BESS systems, designers can choose from three options for ground-fault detection for the DC side:

1. Active insulation monitoring. This approach involves injecting a low-level signal that seeks the lowest-resistance path back to the relay through ground. The leakage current returning to the relay is directly proportional to the insulation of the system to ground. This method is attractive, but has some significant challenges, including difficulty in locating the exact fault location, susceptibility to system capacitance and interference of the active signal with other components of the electrical system.
2. Passive voltage monitoring with respect to ground. This method does not inject an active signal; instead, it monitors the voltage of each side of the DC bus (or each phase of the AC bus) with respect to ground. The advantage is that there is no active signal to cause any interference, but fault location is a challenge with this method as well.
3. Passive current monitoring through use of a ground neutral ground reference. The Littelfuse SE-601 Series DC Ground-Fault Monitor (Figure 2) can provide such a reference. This approach creates a neutral ground point in between the DC bus voltages and looks for leakage current to or from ground. The advantages of this system are that the fault location (positive or negative DC bus) can be determined, there are no active signals to cause interference, and the reference module usually serves to limit fault currents to a safe value. The disadvantage of this method is that a symmetrical fault (a fault of equal resistance to ground on both buses simultaneously) might not be detected.

Any current running through to ground requires attention. Sensitive ground fault-relays will pick up leakage currents at 10 mA or even lower. The latest ground-fault relays can pick up levels of fault current as low as 30 milliamps. Typically, a ground reference module is installed between the negative and positive portions of a DC system, the reference model is connected to the relay, and the relay is connected to the ground.

Although most BESSs are ungrounded, grounded BESSs do exist but require different methods of ground-fault detection. Designers need to weigh the relative merits of an AC ground-fault relay vs. an AC insulation monitor. An AC ground-fault relay, such as the SE-704 Earth-Leakage Relay (Figure 3), offers very sensitive ground-fault detection and can be used on systems with significant harmonic content. The output contacts can be connected for use in protective tripping circuits or in alarm indication circuits. The analog output can be used with a PLC or a meter.

In contrast, an AC insulation monitor such as the PGR-3200 Series Insulation Monitor (Figure 4) which operates on one- or three-phase ungrounded systems up to 6 kV, can also be used on grounded systems to monitor the insulation for damage when the system is de-energized.

Many designers choose to use a breaker between each battery bank and the combiner box to simplify performing inspection or maintenance on each bank individually. An ungrounded DC ground-fault monitor, such as the Littelfuse SE-601 Series, can be used to monitor the status of the battery banks. It can be used in combination with the EL3100 Ground-Fault and Phase-Voltage Indicator (Figure 5) for 3-phase systems. It meets both the NEC and CE Code requirements for ground detectors for ungrounded AC systems.

Arc-flash protection

According to OSHA, arc-flash events are responsible for approximately 80 percent of electrically related accidents and fatalities among qualified electrical workers. Even when there are no injuries to workers, an arc flash can destroy equipment, requiring costly replacement and system downtime.

The high levels of DC power that feed into inverters from the combined output of the banks of DC batteries creates the potential for arc-flash incidents. When the outputs of multiple daisy-chained batteries are brought together in a combiner box, they can also produce sufficient DC voltage to initiate an arc. Unlike with sinusoidal AC power, where the zero crossing helps AC arcs extinguish themselves, there’s less chance that DC arcs from batteries will be self-extinguishing,

Arc flashes present a number of hazards. The heat can be more intense than the temperature on the surface of the sun, and the accompanying explosion may hurl debris at the speed of a bullet. The threat to both maintenance personnel and nearby equipment is obvious. To mitigate these hazards, arc-flash relays are designed to detect the light from an emerging arc flash and trip an upstream circuit breaker as quickly as possible. For example, the PGR-8800 Series Arc-Flash Relay (Figure 6a) can detect and send a trip signal in less than 1 millisecond, preventing an arc from growing into a potentially catastrophic incident. The trip time for a typical AF0100 Series Arc-Flash Relay (Figure 6b) configuration is less than 5 milliseconds.

Installing an arc-flash relay system involves placing light sensors around the interior of the enclosure that houses the inverter and the associated bus bars most likely to be the origin of an arc. The power semiconductor device inside the inverter usually fails safe, but it is possible that it or its connectors could fail to ground and cause an arc flash.

Arc-flash considerations for DC and energy storage applications

Allow calculating the arc flash potential for to develop the calculations for arc-flash incident energy on, particularly the development of IEEE 1584 (Guide for Performing Arc-Flash Hazard Calculations). A revision is forthcoming based on further testing with AC systems. However, DC arc flash has been less studied and is less understood. The DC fault currents can be released rapidly on almost all types of BESSs, but those employing lithium-ion batteries can release very large amounts of current very rapidly.

The purpose of arc-flash calculations is to determine the largest possible incident energy. However, a few factors that may not be intuitively obvious can result in higher incident energy levels than would be anticipated if only an overcurrent protective device were used. These factors include:

• Battery age: As batteries age, their internal impedance increases. This can result in lower arc-flash current, which can in fact lead to higher energy because the overcurrent protection device takes longer to operate.
• State of charge: A partially depleted battery bank may not produce full arcing or short-circuit current. Using an arc-flash relay instead of relying on overcurrent protection devices alone for arc-flash protection can help designers realize a consistently low incident energy throughout the lifetime of the BESS.

It’s also important to keep in mind, for incident energy calculations, that battery cabinets tend to direct the energy out of the cabinet door. Large-scale BESS enclosures can expose personnel to even more energy during an arc flash, both by containing the fault and by making it more difficult for workers to self-rescue within a typical two-second window.

The battery banks themselves represent an arc-flash protection challenge in a BESS. An arc flash on one battery bank will be fed from other parallel battery banks. This can be resolved by monitoring the battery bank and disconnecting them from the bus on a fault. At this point, the arc fault is only fed from the faulted bank, reducing its total energy by a factor proportional to the total number of parallel battery banks. The remaining battery banks will continue supplying, or being supplied with, energy. Although disconnecting a faulted bank has a significant impact on operations and reducing incident energy, a fault local to the battery bank is more difficult to address. One option is to provide the means to disconnect/ de-couple sections of the battery bank physically, further reducing the voltage of each remaining section and reducing the hazard and available incident energy while maintenance is being performed.

How Littelfuse can help

Littelfuse is committed to helping BESS integrators ensure that their circuit protection strategy is complete. In some cases, Littelfuse can modify standard circuit protection products to fit an application’s unique requirements. Littelfuse personnel also work with BESS integrators to review their circuit protection plan and ensure it makes sense for the specific application and provides adequate protection for both equipment and workers. By walking integrators through the advantages and costs of the various options available, Littelfuse can help them make informed, cost-effective choices for specific products and locations.

To support the growing BESS market, Littelfuse will provide this expert design assistance at no cost to the system integrator. To request Littelfuse help in creating a comprehensive circuit protection strategy, integrators need only supply some basic information: all voltage levels each circuit will see, the nominal currents each circuit will see in steady state, the available short-circuit current, and the time constants of the application (based on the inductance to resistance ratio).

Visit TTI to learn more about how Littelfuse can help you develop a BESS circuit protection strategy.

The post Battery energy storage systems demand a comprehensive circuit protection strategy appeared first on Engineering.com.

Written by: Ryan Smart, Vice President of Product, Harwin

Electrically powered vertical take-off and landing (eVTOL) aircraft are shaking up the aerospace industry. The trend is similar to the effect that electric vehicles (EVs) have had on the automotive market. This article explores the requirements of eVTOL applications, focusing on battery management and power and signal connectivity. The area is of vital importance, as the aircraft need detailed data about the onboard battery/powertrain system to run safely.

According to McKinsey, eVTOL has attracted $12.8 billion in investment over the last 12 years. Currently, around 200 companies worldwide have development projects in the sector.

eVTOL is suitable for various applications, but the most popular one is urban transportation. Aerial taxis will offer faster, greener and more efficient transfers from city locations, such as financial quarters, to airports. eVTOLs could replace the helicopter services currently used for this purpose.

eVTOL-based transportation will also be more cost-effective. Aviation fuel costs are constantly increasing, but most eVTOL aircraft don’t require any fuel. There are also other commercial and logistical benefits. The first of these is noise: eVTOL will help reduce noise pollution. At the moment, this is the main factor restricting helicopter operation at nighttime. With eVTOLs, however, commercial flights could potentially run 24/7. Replacing helicopters could also improve air quality in city centers, as eVTOLs don’t generate air pollution.

Key engineering design considerations

Unlike conventional aircraft, eVTOL must deliver vertical and horizontal propulsion. The movement can be achieved with fixed vertical rotors for take-off/landing and horizontal ones for moving forward. Alternatively, the rotors can use actuators to move between vertical and horizontal flight configurations.

Powering the constituent electrical actuators is another critical function. These actuators control the aircraft roll moment by deflecting aileron surfaces and pitch moment by deflecting the elevator. Yaw moment is managed through rudder deflection and thrust force by changing the propeller speed. The aircraft designs must also incorporate the infrastructure for distributing power to electric-propulsion motors, positioning systems, tele-networking and cockpit/mission systems.

As eVTOLs are smaller and lighter than conventional aircraft, they are also less stable. While traditional aircraft become lighter during flight as they burn fuel, eVTOLs don’t. They remain the same weight throughout the flight, which puts more stress on the structure during landing. These requirements need to be built into the design. This means using robust materials in the airframes as well as electrical components.

Importance of battery monitoring in eVTOL designs

eVTOL aircraft are powered by large Li-ion batteries. Therefore, an effective battery management system (BMS) is essential. Data relating to current, voltage, temperature and other parameters must be continuously available to ensure optimal performance and safety of the passengers. If a battery fault that should have been detected leads to an accident, the aircraft manufacturer or operator could damage their reputation beyond repair.

In an electric road vehicle, managing risks is more straightforward. The EV can automatically stop and alert the occupants if there is a risk of thermal runaway within the battery. For eVTOLs, it is not as simple. When a fault occurs, the aircraft could be thousands of meters up in the air. Likewise, if a cell malfunctions and goes offline, the effect might be severe. In a ground vehicle, it will mean a loss of traction. But for an eVTOL, a power failure could result in a sudden drop in altitude. That’s why BMS monitoring of the cells needs increased scrutiny to identify and mitigate potential problems as quickly as possible.

What to look for in a connector

The connectors used in eVTOL BMS implementations need to be chosen carefully. Here is a summary of what engineers should consider:

Compactness: eVTOLs are dependent on electrical propulsion, so the components need to be small. They must take up minimal board space and have low profiles.

Contact density: eVTOLs’ battery packs feature many Li-ion cells. Compact connectors with dense contact arrangements help achieve data acquisition more easily.

Weight: eVTOL designs have strict weight constraints, so the fuselage and hardware must be as light as possible. The same goes for the components used. Light construction helps maximize the number of passengers or the amount of cargo the aircraft can carry.

Reliability: To guarantee passenger safety, the connectors must function over a prolonged operational life without failure.

Robustness: The connectors must maintain continued operation in harsh working conditions. They will have to withstand shocks, vibrations and extreme temperatures.

EMI susceptibility: Due to proximity to electrical sources, the designs must consider electromagnetic interference (EMI). Overlooking the issue can result in poor data quality, which can affect the decisions made by the BMS.

Component expense: As the eVTOL sector is very cost-sensitive, keeping the bill-of-materials (BoM) down is vital. This, combined with the low volume levels, means that custom-built components are not an option. Instead, companies must have access to off-the-shelf products to optimize their budgets.

Quality: Complete output repeatability in the production process is paramount when supplying parts to the aerospace market. Any variation could have dire consequences. That’s why it’s essential to work with connector suppliers that conform to globally recognized quality standards.

Picking the most applicable products

Harwin has a long history of providing aerospace OEMs with high-reliability (Hi-Rel) connectors. Committed to quality engineering, its manufacturing facility is certified per EN9100D/AS9100D quality standards. When working with the eVTOL sector, the Harwin team benefits from experience with unmanned aerial vehicle (UAV) projects. Regarding size, weight and robustness, the connectors used in UAVs have similar requirements to those used in eVTOLs.

Optimized for use in various eVTOL systems, the 1.25mm-pitch Gecko connectors deliver powerful performance and reliability. The lightweight and compact components have 2A-rated contacts made from a durable Beryllium-Copper. The patented 4-finger design means that interconnections remain unaffected by even the most intense shocks and vibrations.

Some applications, such as eVTOL BMS installation, require a larger number of contacts and large signal currents. Here, Harwin’s Datamate 2mm-pitch Hi-Rel connectors offer significant advantages. They are available in single, dual and triple-row configurations. Like the Gecko series, they provide industry-leading resilience to harsh environments. This means withstanding shocks of up to 100G. Their contacts can carry 3A of current (3.3A on an individual contact). A choice of latching mechanisms makes it easy to find the best match for the available space or the operating conditions.

Gecko and Datamate connectors can come with integrated back shells to combat EMI issues. Cable assemblies are also available to accompany them. They are available in any length and configuration, even for small quantities. Harwin also offers Mix-Tek versions of both connector series. These devices make it possible to address power and data signals with just one component, saving space and simplifying design layouts.

Conclusion

eVTOL will offer an environmentally friendly and more economical way of providing short-hop flights. The lower costs and 24/7 operation could make it accessible to more people. Battery reserve and performance will be central to eVTOL services, and will also provide manufacturers with a way to differentiate their models in a competitive market. Recharging speed and the distance the aircraft can travel before recharging will be key differentiators. These requirements highlight the role of the BMS function in boosting battery performance and extending its longevity. Finally, having superior BMS interconnects means that accurate data is always available. This helps maintain optimal safety in eVTOL aircraft.

To learn more, visit TTI and Harwin.

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Radar systems are continuously evolving as threats become more diverse. These systems are expected to register anything from drones to hypersonic missiles. As a result, modern radars are becoming more agile. Increasingly, that means they rely on a multifunction array (MFA), where one array can be used for search, track and targeting as well as electronic warfare and communications functions.

The need for a single-array configuration, paired with the desire to improve signal-to-noise ratio (SNR) with an analog-to-digital converter (ADC) on every antenna element, was a catalyst for the adoption of fully digital beamforming.

With fully digital beamforming, shown below, each antenna element can transmit and receive multiple beams or split them in different directions simultaneously without interference. In addition, each element is software-defined, so control and tuning can occur on an application-specific basis. Designs that leverage fully digital beamforming use space more efficiently while achieving more comprehensive radar coverage.

Radar systems and other military applications have always been restricted by size, weight and power (SWaP) requirements. Now, engineers are up against additional size constraints to support electronics with fully digital beamforming. In addition to managing higher power consumption, integrated devices must fit in a denser phased array with an antenna pitch measuring half the wavelength (i.e., λ/2) or less for optimal array performance. Wavelength decreases as frequency increases, so size requirements only become more restrictive in high-frequency applications.

Under these conditions, there’s a variety of components that must fit into a smaller amount of board space. Here are some component selections that deserve special consideration:

Energy storage capacitors

Energy storage capacitors in radar T/R modules support pulsed operation in power amplifiers, and with high-performance expectations and little space, these passive devices are especially SWaP-challenged. Low-profile aluminum electrolytic capacitors like the MLPS Flatpack series, designed and manufactured by Knowles Precision Devices’ subsidiary Cornell Dubilier, offer high capacitance density in a flat configuration for space-saving. These military-grade capacitors are optimized for 10,000 hours at 105 °C, making them ideal for T/R modules and other system electronics that maintain high performance and reliability in a small footprint.

Wideband filters

Wideband filters with high rejection are similarly challenged by strict SWaP requirements. To protect the receiver, these filters must be positioned at every element, and as mentioned above, they must be sized at λ/2 or less to fit in the phased array antenna pitch.

Knowles Precision Devices’ 10 GHz surface mount bandpass filters support direct sampling receivers enabled by high-speed RF-ADCs. With deep expertise in high-reliability ceramic devices, Knowles Precision Devices fabricates its DLI brand filters on high-k ceramic substrate materials to achieve high performance in a footprint smaller than λ/2.

Bypass capacitors

Fully digital beamformers often include devices, like low-noise amplifiers, that can be implemented as high-frequency monolithic microwave integrated circuit (MMIC) dies. MMIC amplifiers with broadband gain need protection from RF noise on the supply line. Bypass capacitors offer an efficient path for RF energy to ground before it enters a gain stage. Look for wire-bondable microwave capacitors (rather than surface-mount) that can provide the right amount of capacitance at a high operating voltage for MMICs in high-frequency applications like radar.

High Q capacitors

Q factor, or quality factor, is a figure used to rate and compare multi-layer ceramic capacitors (MLCCs) based on merit. It’s expressed as the ratio between stored energy and lost energy per oscillation cycle. In resonant circuits, power loss is accounted for via the equivalent series resistance (ESR). Higher ESR indicates higher losses in the capacitor. In high-frequency applications, maintaining efficiency and reliability at the component level is an important contribution to performance optimization. MLCCs built with high Q material are specifically designed to overcome this design challenge.

High Q MLCCs will have a low εr value, and they’re generally built in the pF range to mitigate power loss and minimize the likelihood of overheating. High frequency and low power loss are critical parameters for radar systems. Consider MLCCs based on high Q dielectrics to ensure high performance. Knowles Precision Devices offers ultra-low ESR, high temperature, high power, ultra stable and leaded options.

High-reliability capacitors

Radar systems subject components to intense operating conditions. To ensure quality and performance over time, they must face testing at elevated conditions. Manufacturers perform accelerated life cycle testing to better inform you of a component’s limitations. For example, chip capacitors and dielectric formulations undergo burn-in or voltage conditioning to assess their reliability at a specific voltage and temperature level for a duration of time. Capacitors that fail this test usually lose resistivity under these conditions early in the test cycle.

Common high-reliability military specifications, including MIL-C-55681, MIL-C-123 and MIL-C-49467, each have their own applicable specifications for reliability testing. Work with a manufacturer that has the experience and capacity to run and document these tests. Knowles Precision Devices typically uses a test voltage that is twice the working voltage rating of the device, at 85°C or 125°C for a duration of 96, 100, or 168 hours of test time, and maintains the capacity to process approximately four million parts per month to uphold strict screening criteria.

Supporting innovation in radar systems

While many manufacturers can accommodate MIL-level screening and high-reliability applications, Knowles Precision Devices has designed and tested to these standards for decades with no field failures. The support of an experienced component design and manufacturing company with custom capabilities and extensive testing equipment is key to the continued success and advancement of radar technologies. Whether you’re working with a cutting-edge system or legacy equipment, every component selection makes a difference, so leverage a component manufacturer’s expertise. Knowles Precision Devices’ engineering team monitors current trends that impact your design needs and adapts accordingly, so your team can focus on the core research and development efforts at hand.

For more information on off-the-shelf or custom components for radar or other high-reliability systems, contact Knowles Precision Devices to connect with our engineering team.

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Executives and decision makers know it’s not easy to automate industrial processes, but what they may not understand is why. The challenges arise from the fact that most facilities are made up of bespoke machines used to make specific parts, products or assemblies. Hence, there is rarely a one-size-fits-all solution.

Obvious examples of this phenomena can be seen with grippers, effectors and tools that physically interact with products or parts. This equipment must be tailored to hold, move and manipulate an object with specific geometry. But specialization doesn’t end there. An often-overlooked piece of customized equipment are industrial automation control panels. Afterall, if the control panel operates custom machinery, it makes sense that it also needs to be customized.

But these modifications aren’t easy. A search of Jameco, a supplier of industrial automation parts, for products only from MEAN WELL, which is just one of their manufacturing partners, comes up with almost 6,400 results. So, how does anyone make sense of it all?

To understand control panels and how one would go about customizing them for a particular application, engineering.com sat down with Gil Orozco, vice president of Product Management at Jameco and Harland Chen, field application engineer at MEAN WELL.

What is an industrial automation control panel?

Industrial automation control panels act as a central hub for all the components and tools used to monitor, instruct and integrate machinery. “Industrial automation control panels are the backbone of automation,” says Chen. “Panels enhance the efficiency, productivity, safety and quality of the system.”

Just like the machines they operate; panel parts need to be uniquely selected to meet particular needs. “The specific components used will depend on the intended function and complexity of the control panel,” confirms Orozco. “Customer applications are endless. [Selecting the right components] depends on what the customer requires.”

Even though contents can vary, control panels typically consist of:

• Circuit breakers and fuses, which cut the power supply in the event of excess current or faults in the system. This is done to protect other circuitry.
• Switches and/or buttons, which make up parts of the human machine interface (HMI) that enables human operators to manually control or preset operations.
• Indicators, which contain LED lights, computer monitors and gauges. These HMI parts are used to keep human operators informed of the status of the facility’s equipment.
• Power supplies, which includes the electrical batteries, generators and/or grid connections needed to ensure components operate.
• Control relays, which help control high-power devices or circuits with low power signals.
• Terminal blocks, which provide access points to connect and secure wires and cables.
• Programmable logic controllers (PLCs), which are advanced automation and control circuits used to manage equipment and systems based on measured inputs and code.

With the rise of Industry 4.0, many of these control panel components have become smarter. They can communicate with digital systems, connect to the Industrial Internet of Things (IIoT) and even digest data, predict performance or make decisions on how to operate. “The components are really in some respect endless,” says Orozco. “In some [instances], you have very smart components [and others] where you have some very basic analog components. So, it really starts with the customer’s application. How we make sense of all that depends on what the customer needs and how can we support them.”

In other words, each of the above parts must be optimized to the task being controlled by the panel. And since there are hundreds, maybe thousands of options for each part, engineering expertise is needed to ensure the panel is optimized to its needs.

What role do control panels play in industrial automation?

Control panels act as the brain and central nervous system of an automated facility. They regulate and manage systems using hardware, software and input data from HMIs, sensors, cameras and more. A control panel need not be fully automated. Some require human interactions, others can be autonomous, and many fall somewhere in between.

Chen explains, “By integrating the programming logic controls, the human machine interface … and various sensors and alternators, the control panels enable the real-time data acquisition and a precise control of the industrial operation.”

So, the benefits of the fully automated systems are that they offer consistent, precise and accurate control. In contrast, systems with human interactions may involve industrial operations that can be more unpredictable, requiring the oversight of human operators who can quickly adapt to a situation.

Automation control panel safety, compliance and regulations

Strict safety, compliance and regulation standards exist to prevent control panels from causing electrical shocks, fires and damage to people or property. “The control panel must adhere to this compliance and regulation to ensure safe operations,” Chen explains. Control panels require “electrical safety, proper grounding and protection against flash cases. Compliance with standards like UL 508A in the U.S., or ‘CE markings’ in Europe and the CSA certification in Canada are essential.”

He also notes the importance of ensuring the electronics operate at safe temperatures, meet environmental safety requirements and have ingress protection (IP) ratings — which measures how well an electrical device is protected from water or dust.

Since so much customization comes into play when finding the right automation control panel, ensuring that it meets safety, compliance and regulation standards is not easy. So once again, engineering expertise is required to guarantee success.

Engineering expertise for industrial control panels

Jameco offers almost 60 different DIN rail terminal blocks from MEAN WELL alone. When other manufacturing partners are included in the search, the number increases by a factor of three.  So, how does anyone know which control panel parts are needed for their particular setup?

Chen and Orozco suggest contacting Jameco and MEAN WELL directly. “It boils down to the customer’s needs,” says Orozco. “Applications and components are endless and there are many different brands and options … We need to understand the [given] application to provide a solution to the customer. And that’s where Jameco and MEAN WELL come in … We take an approach to understanding the customer’s requirements to show what total solutions we can offer them.”

Chen used the example of sizing a power supply. “The power supply we evaluate is based on the necessary functionalities of the [given] control panel. We consider the components, space [and] installation of the power supply.”

With the help of Jameco and MEAN WELL, manufacturers can make sense of all the available options, components and customizations they can add to their control panels. Instead of being lost in a forest of part numbers and compliance documentation, they will see a path to the right solution for a given situation.

“We evaluate based on the region, power and customer,” adds Chen. “If the customer needs to meet a specialized safety standard, our factories in China and Taiwan offer the certification needed for the specific safety and power supply standard.”

For more information on automation control panels solutions, read more about industrial power components.

The post Customizing automation control panels is challenging, but skipping it is worse appeared first on Engineering.com.