BASIC KNOWLEDGE - EMC Basics for electromagnetic compatibility (EMC) of power electronics

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As more and more wirelessly connected devices hit the market, thanks in part to the growth of the Internet of Things (IoT), electromagnetic compatibility is of growing importance.

Electromagnetic compatibility (EMC) is an important concept of electrical engineering.

It is the ability of electrical systems to function in their electromagnetic environment by limiting the unintentional generation, propagation, and reception of electromagnetic energy which could cause effects such as electromagnetic interference (EMI) or physical damage. Put more simply, it is the concept of enabling electronic devices to operate without mutual interference.

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With the huge growth of wireless electronic devices into everyday life – it’s not just smartphones anymore, but washing machines, televisions, ovens, electric and autonomous vehicles – there exists lots of potential for devices to interfere with one another. This is because electronic circuits can pick up and be compromised by electrical interference.

The basics of EMC and EMI

The point of EMC measures is to ensure that electronic equipment can operate in close proximities without any unwanted interference, known as EMI. EMC has two primary elements:

• Emissions – EMI emissions refer to the generation of unwanted electromagnetic energy. This must be reduced below defined limits to guarantee zero disruption.

• Susceptibility and immunity – An electronic device’s susceptibility to EMI is the way it reacts to this unwanted electromagnetic energy. A big part of circuit design is ensuring a sufficient level of immunity against this.

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Towards an EMC compliant design in power electronics

Towards the end of the 20th century, EMC levels were relatively low, however, noticeable disruptions could occur – a classic example is interference caused by GSM cell phones when used near speakers. Since this time, however, EMC levels have grown and an increased awareness, plus the desire of manufacturers to maintain high standards, has led to the introduction of EMC standards. Today, EMC is an integral part of any electronic design project, and standards are implemented and enforced worldwide.

The evolution of EMC standards

Some of the first EMC standards were introduced around 1980 when the U.S. Federal Communications Commission (FCC), in response to the growing availability of digital systems, imposed legal limits on EMC from all digital equipment to prevent interference with radio communications and broadcast equipment.

At around the same time, European legislators introduced the EMC Directive. This applied to all equipment sold on the market in the European Community that was "liable to cause electromagnetic disturbance or the performance of which is liable to be affected by such disturbance." This later evolved into the now well-established EMC standard.

Today, there are hundreds of common EMC standards that are used worldwide.

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Achieving compliance with EMC standards through design

Because EMI can prevent adjacent pieces of electronic equipment from working, electronic design must account for EMC from the outset. With the vast growth in the usage of electronic equipment, there is a great necessity to design for EMC from the outset of a new project and implement the various EMC design techniques into the end-product’s whole concept.

When designing electronic circuits, therefore, it is important to take precautions to ensure that EMC performance requirements can be met. Trying to fix any EMC problems once a circuit has been built will be extremely difficult and expensive. Areas to address during the design stage to ensure optimal EMC performance may include circuit design for minimum radiation, EMC filters, circuit partitioning, and grounding, amongst other things.

At the end of any electronic product’s design stage, EMC testing must take place by law. There are many examples of products from many well-known manufacturers that have been pulled from the market because they did not meet EMC standards. If thorough testing had taken place, this would never have happened.

In the UK, for example, stringent laws have been in place since 1992 which force all manufacturers and importers of electronic products to ensure that they are electromagnetically compatible.

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