Addressing EMC Challenges in Electric Vehicle Supply Equipment

Globally, electric vehicle supply equipment (EVSE) has doubled in the past three years. The last count in 2020 showed 1.4 million¹ charging points across the globe. This market is set to cross $14 billion in 2026, a compound annual growth rate of 36 percent over the next five years. This momentum is fueled by growing demands in various markets, underpinned by incentives for car buyers to switch to electric transportation and policies driving zero emission goals.

In the U.S., which trails China and Europe in electric vehicle (EV) adoption, the Biden administration unveiled the Bipartisan Infrastructure Framework² in June to help automakers boost production of EVs. Plans include a boost of $7.5 billion for public charging infrastructure, with the goal of adding 500,000 EV chargers by 2030. At the consumer end of this complex e-mobility ecosystem, electric car drivers expect to drive up to any charging point to charge their batteries as easily as they can fill their gas tanks in current combustion engine cars.

EVSE suppliers certainly have this impetus to ride the global time-to-market wave, requiring some new technology challenges to be tackled: safety, performance and interoperability among electric cars and the charging stations. With expectations of faster and higher power charging comes the need to ensure safety and performance, across an increasing range of car models and EVSE vendors. A key area is ensuring electromagnetic compatibility (EMC) of the EVSE, with the vehicles they will charge and the plethora of electronic devices that rule modern life. With more charging stations sprouting across cities, especially near residential areas and schools, EMC standards are evolving to protect both the public and industry. For EVSE makers, ensuring their products comply with these standards supports product safety, performance and reliability—at the same time building market confidence and brand reputation.

Before discussing the implications of electromagnetic interference (EMI) in the EV charging environment and why EMC conformance testing is so important, let’s define two common acronyms:

• EMI: electromagnetic disturbances that degrade the performance of electronic or electrical equipment
• EMC: the capability of electrical and electronic systems and devices to operate in their intended electromagnetic environment without unacceptable degradation from electromagnetic interference.

WHY IS EMC TESTING SO IMPORTANT?

A charging station can produce radiated emissions caused by electromagnetic waves radiated into space while the charging station is being used. It can also produce conducted emissions from the voltage and current in the power cable. This EMI can potentially disrupt the proper functioning of other electromechanical devices and wireless communications and may pose health risks to people. With the convergence of connected autonomous driving technology and electric cars, it is vital that the EVSE is tested to identify and correct any interference with the onboard safety and communication systems.

In an interesting study,³ researchers from the Technical University of Munich (TUM) measured the electromagnetic fields of EV and EVSE and the impact on pacemakers inside cardiac patients. The largest electromagnetic field detected was along the charging cable during high current charging: 116.5 μT. The field strength in the EV cabin was lower: 2.1 to 3.6 μT. Fortunately, the research found no change in the functioning of the pacemakers; however, with both EV and EVSE technology constantly advancing, the TUM researchers advised caution for these patients when outside the car, for instance during charging around Level-2 (240 V) and Level-3 (400 V) charging stations, which use high electric current.

MULTIPLE EMC STANDARDS

EVSE manufacturers must meet several EMC regulatory requirements and certifications before releasing products to market. For instance, the European IEC 61000 EMC standard defines limits to provide reasonable protection against harmful interference. This is the directive that addresses EMI issues for EV charging infrastructure products. In the U.S., EMC compliance is regulated by the Federal Communications Commission. Class A limits cover commercial, business and industrial environments, while Class B, the more stringent category, covers EVSE in residential areas (see Table 1). In Canada, the ICES-003, Section 5 standards require EV charging station providers operating in areas with exposure to the public to have Class B compliance. If a charging station does not have Class B certification, it must display a warning label to caution users that magnetic fields around it can be problematic. This does not bode well if an EVSE supplier aims to gain market confidence.

Other key charging and EMC norms and standards include the following:

• IEC 61851-21 – This is an EMC product standard that specifies the limits of emission and immunity (i.e., the minimum test levels) for electric road vehicle charging systems.
• IEC/CISPR 11, EN 55011 – This standard covers emission requirements related to RF disturbances in the frequency range from 9 kHz to 400 GHz.
• TL 81000 – This covers the EMC requirements for electronic components in motor vehicles.

MEASURING EMC COMPLIANCE

Ensuring EVSE meets safety and performance requirements requires having comprehensive compliance test processes and reliable test and measurement equipment. These are the essentials to measure the causes and impact of electrical noise, enabling engineers to define, debug and circumvent EMI causes and effects. In addition to EVSE circuitry, user interfaces such as touch screens, displays and wireless communication interfaces, such as those used for contactless payment, must be thoroughly tested against both conducted and radiated emissions. To meet these evolving conformance standards and regulations, EVSE manufacturers must plan test capacity and the capability to handle increasing test complexity while planning their design, development and production cycles (see Figure 1).

Figure 1 Capabilities of an EMC test lab. Source: Keysight EMC Test Lab.⁵

In today’s competitive e-mobility market, EVSE manufacturers must adapt quickly to test a wide range of EVs to ensure their charging products conform to the necessary standards, which differ around the world. In many cases, the EVSE manufacturer does not have access to detailed information about how the EV manufacturer has implemented its controller or if it complies with the published standards. For this reason, a holistic compliance test requires a “synthetic” setup which emulates the real-world environment of a charging station, operates within the appropriate specifications and provides appropriate means of defect detection and analysis. This real-world emulation test environment provides further advantages:

• A real electric car is not needed in the test lab. The emulator simulates the specifications of different EV models.
• The charging duration is not restricted, as an electronic load is used instead of a battery with limited capacity.
• Tests can be fully automated, which is particularly useful with recurring test sequences and large numbers of units, such as with end-of-line testing.

A key consideration for EMC testing in this emulated environment is whether the test equipment itself is properly shielded so it provides “unbiased” measurements necessary for EMC compliance and homologation tests.

The EMC test architecture illustrated in Figure 2 shows an EMC-optimized emulator, the Keysight Scienlab Charging Discovery System (CDS), which is configured in this use case to act as an electric car for testing EVSE. Both the emulator and the EVSE device under test (DUT) are inside an anechoic chamber for the EMC immunity and emission tests of EV charging infrastructure, such as DC fast-charging stations or AC or DC charging.

Figure 2 Test setup for EMC testing of the EVSE. Source: Keysight Scienlab CDS.⁶

Due to the special EMC shielded design and built-in low noise components, emission from the emulator is reduced to a minimum. This enables EMC testing of EVSE under real charging conditions without environmental interferences. Since the emulator is immune to external electromagnetic fields, it can be placed close to the EVSE DUT during immunity testing.

OUTLOOK

Demand for EMC testing is likely to grow in the coming years, buoyed by market drivers such as faster and higher power charging and the convergence of connected automated driving features on the e-mobility platform. While new conformance standards and regulations may pose challenges for EVSE manufacturers, they have opened opportunities for companies offering EMC testing and certification services. This collaborative approach is a win-win for the industry, allowing EVSE manufacturers to focus on developing and deploying a safe, reliable charging infrastructure as part of building a zero carbon footprint transportation future.

References

1. C. McKerracher, “EV Charging Data Shows a Widely Divergent Global Path,” Bloomberg, March 2021, Web. www.bloomberg.com/news/articles/2021-03-23/ev-charging-data-shows-a-widely-divergent-global-path.
2. “FACT SHEET: President Biden Announces Support for the Bipartisan Infrastructure Framework,” The White House, June 2021, Web. www.whitehouse.gov/briefing-room/statements-releases/2021/06/24/fact-sheet-president-biden-announces-support-for-the-bipartisan-infrastructure-framework/.
3. “Electric cars: No restrictions for patients with pacemakers and defibrillators,” Technical University of Munich, June 2018, Web. www.tum.de/en/global/international-locations/san-francisco-news/news-detail/article/34776/.
4. “EMC Regulations,” LearnEMC, Web. https://learnemc.com/emc-regulations-and-standards.
5. “Regulatory Test Test Lab, Böblingen Germany,” Keysight Technologies, Web. www.keysight.com/us/en/products/services/test-as-a-service-taas/emc-test-lab.html.
6. “SL 1040A Series Scienlab Charging Discovery System (CDS),” Keysight Technologies, Web. www.keysight.com/us/en/products/hev-ev-grid-emulators-and-test-systems/sl1040a-series-scienlab-charging-discovery-system.html.