Designing for Electromagnetic Compatibility in Power Electronics

December 11, 2019 , in Blog, Industrial

In industry, there is no substitute for delivering a product that meets its performance specifications to the end-user. Not doing so will, at a minimum, have a negative impact on the number of customers that use your product. Additionally, this will obviously decrease your return on investment (ROI) and may expose you to legal proceedings and possibly financial sanctions from your dissatisfied customers. The best way to avoid these outcomes is to deliver a product that at least meets its expected quality (performance and reliability) or what is most often referred to as the minimum viable product (MVP).

Achieving an acceptable result

Minimum viable product

As with most PCB development, the design, manufacturing, and test (DBT) of industrial PCBs is an iterative process to improve quality. For industrial electronics, arriving at a high-quality board or electronic device is not sufficient, unless the development process also includes consideration of environmental concerns that may have a significant impact on performance and reliability. These concerns include thermal variance, exposure to moisture, motion and vibratory requirements, and EMI. For electromagnetics, elimination is usually not possible; therefore, the objective should be to achieve electromagnetic compatibility in power electronics for PCBAs. Let’s define EMC in industrial production environments and then discuss how it can be achieved.

What is Electromagnetic Compatibility in Industrial Production Environments?

According to the FDA, electromagnetic compatibility can be defined as follows:

“Electromagnetic compatibility, or EMC means that a device is compatible with (i.e., no interference is caused by) its electromagnetic (EM) environment and it does not emit levels of EM energy that cause electromagnetic interference (EMI) in other devices in the vicinity.”

For practicality, this definition should probably be refined or qualified to an electronic device does not emit or is not susceptible to levels of EMI that will distort or harm the functionality of the device or any other device in its environment. Thus, it is necessary that your board not contribute to the EMI in its environment nor allow environmental EMI to affect its operation. For EMC, it is best to view these two conditions separately, as listed below.

Types of Industrial Electromagnetic Interference (EMI)

Susceptibility - In today’s automated industrial facilities PCBAs are typically embedded in machinery or equipment in the vicinity of other boards; including power supplies and motor controllers that may emit radiation. For EMC, it is desirable to minimize the effects of this type of EMI on your board’s functionality and operation.

Emission - Installing devices in close proximity to minimize material and energy costs is a constant objective for equipment designers, just as it is for electronics OEMs. However, locating electronic devices, especially those with RF devices or electromagnetic radiators, near each other presents EMC problems. And minimizing your board’s contribution to the environmental EMI should be a primary goal.

Meeting these requirements can be considered to be the MVP for EMC in an industrial environment.

Achieving Electromagnetic Compatibility in Power Electronics Systems

Industrial environments present challenges that are uncommon for other circuit board applications. And design considerations must include choosing the best materials for high voltages and accommodating high currents. In order to process these high voltages, currents and powers power electronic devices are used. Generally, a power electronics device can be any device used to generate or propagate high power signals. Typical devices include switches, amplifiers, relays, power converters, and cables. All of these are sources of radiation that may add to the emission from your board, especially during switching or when spiking occurs.  Devices that are susceptible to receiving radiation or EMI are capacitors, inductors, and even copper traces.

The challenge of minimizing EMI emission and absorption is that this activity may be a natural function of the device. For example, an inductor will create a magnetic field in its immediate environment when a current flows through it. The amount of current determines the field strength and thus the extent of the field from the coil. Fortunately, there are ways to minimize emission and absorption effects and achieve an acceptable MVP for electromagnetic compatibility in power electronics for your boards, as presented below.

Designing for Emission EMC in Power Electronics

⇑ Ensure your device adheres to FCC regulations

Designing your industrial PCBA should include determining if your board includes RF devices that are radiators according to FCC Title Chapter 1 Part 15. If your board is intended for an Industrial IoT (IIoT) system, you should also make sure to follow FCC regulations for building IoT devices as these will impact your design.

⇑ Use shielding

If your board contains high current electronics devices that are emitters; such as coils and transformers, shielding should probably be investigated as part of your design. Not only can shielding help you achieve EMC, but it can also help with on board EMI.

⇑ Install board in an enclosure

Since most PCBAs in industrial environments are embedded, it may be assumed that an enclosure is not necessary or will add to the size of the device. Although increased size may be a reasonable concern, the assertion that an enclosure is not necessary cannot be assumed.

Designing for Susceptibility EMC in Power Electronics

⇓ Use shielding and enclosures

Just as shielding and enclosures can prevent EM emissions they can also prevent absorption.

⇓ Follow design rules for minimizing on-board EMI

Once your board absorbs radiation from its environment it becomes an on-board EMI problem and the same design techniques should be used to combat it as for interference that originates on the board. For detailed guidance on applying these, see the articles below:

Tempo‘s Industry 4.0 Custom PCB Manufacturing Services
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Achieving electromagnetic compatibility with your board’s industrial environment is essential for the best performance and reliability. At Tempo Automation, we are well-equipped to assist you in developing PCBAs that will adhere to the EMC for the intended facility. In fact, maintaining EMC for our software-driven manufacturing process factory is a primary concern for us.

To help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on CAD files or how to achieve electromagnetic compatibility in power electronics for your industrial PCBAs, contact us.

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