Design considerations for wirelessly charging EVs

Article By : Kirk Palmer

Interoperability, EMC/EMF, and safety are major design considerations for wirelessly charging electric vehicles.

As electric vehicles (EVs) become more popular, and the world becomes more connected, the demand for wireless charging is growing. In fact, many in the industry believe that mastering wireless power transfer (WPT) is one of the keys to greater and faster EV adoption. The ease of charging the vehicle makes driving it a more attractive, convenient option. But as the industry perfects wirelessly charging EVs, there are safety and performance considerations to keep in mind.

During the WPT process, the EV is parked on wireless charging pad, which serves as the EV supply equipment (EVSE). Once the EV and charging station connect, the process begins without the need for a corded connection. Instead, power is transferred through a magnetic resonance field between the charging station and a receiving pad on the bottom of the EV. After connecting, the energy converts from AC to DC to charge the EV batteries. The process is not only efficient, but convenient and, if done properly, safe.

Wireless products that connect with each other, such as EVs and charging systems, rely on devices and components that exchange, share, and interpret data to “talk” to each other. Here, interoperability is critical to ensure systems form an integrated ecosystem within the charging environment, communicating with one another seamlessly.

illustration showing a car charging with wireless technology

Interoperability considerations

Ensuring interoperability requires several considerations and evaluations. Simulation testing can be effective for evaluating scale, security, and reliability while accounting for other devices, interference and data. Usability accounts for end-use and human interactions in the “real world” to ensure that products meets the consumer’s expectations as they interact with other connected products, networks and the overall Internet of Things (IoT) infrastructure.

One of the most straightforward assessments in product development is validating performance. Similarly, benchmark testing evaluates against similar products. Regression testing plays a key role in making sure that previously developed software continues to perform once it has been altered, or when new features are added during development. It also safeguards performance during updates, enhancements, and configuration changes. Finally, cybersecurity evaluations ensure products keep data secure and do not infect other devices.

Testing components for interoperability ensures they will work together in a secure manner, without sacrificing performance. The “plan, do, check, act” assessment approach is the one used by information security management systems for cybersecurity assessments and offers an effective framework for interoperability considerations. Once interoperability considerations are made and testing needs are identified, an approach should be developed to use the four-stage “plan, do, check, act” system to fully assess interoperability.

  • Plan: Identify improvement opportunities within a product and/or its systems. Using this information, identify and mitigate risk, develop an action plan, and effectively address any issues.
  • Do: At this stage, you will conduct evaluations and assessments, collect analytics and data, and document issues and failures. It’s important to keep all the information from this stage on hand for future use, whether that is redesign of the current product or for future projects and product development.
  • Check: Review and analyze results from the previous stages, evaluate current processes and determine causes of failures. Utilize this information to determine whether interoperability is achieved or whether necessary improvements were made, and corrections have worked. As with other steps, documentation is important.
  • Act: Based on the previous stages’ observations and failures, implement changes to whatever did not work and continue practices that did. If problems persist, return to the previous stages until interoperability is met. Continue to reiterate the process until products adequately meet interoperability requirements.

EMC and safety

Along with interoperability, considerations for electromagnetic interference (EMI) and electromagnetic field (EMF) limits are critical.  In an increasingly connected world, it can be assumed that the EVs and charging stations will regularly encounter other electromagnetic fields from other devices. It’s important to ensure that the fields coming from one electrical/electronic device don’t interfere with the function of another electrical/electronic device in the vicinity. This means ensuring the EV and EVSE do not impact each other or other devices and that they are not affected by other electronics devices such as mobile phones, security monitoring systems, and medical devices.

EMC considerations should be made during the product development stage to mitigate risk and reduce EMI in the final products. Assessments should also be run to ensure optimal EMF ranges and performance and function of EVs and wireless charging systems in relation to each other and other electrical and electronic devices.

Next, safety considerations are of utmost importance for the relevant charging components in the EV, the EVSE, and the interface between the two. During the WPT process, safety considerations need to be made for powering the transmission pad, which is wired to the grid, the receiving pad in the vehicle, the vehicle itself, and the EV batteries. It’s important to ensure power is transmitted, energy is converted, and the batteries charge correctly and safely even during varying of environmental conditions such as extreme hot or cold temperatures and water-based events including rain and snow.

Designers and developers will need to ensure that the process happens without incurring shock, overheating, fire or harmful injury to both people and property. Designing products to mitigate risk is important, as is testing components and finished products to industry standards. Running assessments throughout the product development stage is critical to ensuring safety and can help reduce time and costs associated with redesign and re-evaluation of problem areas.

To aid in the development of wireless EV charging, SAE International has created the first global standard that specifies requirements for EV and EVSE. SAE J2954 was introduced in October 2020 to ensure safe and efficient wireless power transfer from grid supply to an EV vehicle without human interaction. It covers systems with an 11-kW universal ground assembly and is designed to help insure interoperability, safety, emissions, and effective wireless communications.

Design best practices

When designing and implementing wireless charging technology in EVs and EVSE, it’s important to be mindful of interoperability, EMC and safety from the early stages of the development process. Knowing the requirements and standards in place is essential to ensuring that products are compliant, and that they fulfill consumer demands and needs. Keeping these items in mind from the start can help avoid time delays and increased costs from product redesign and testing.

Many of these considerations will also help ensure optimum performance as well as meeting industry needs and customer demands. In turn, this helps ensure product success, build brands and enhances manufacturer reputations. Making products that function well, interact and communicate effectively, and function safely will also help advance the adoption of EVs. Wireless charging options that are efficient and safe can make a difference in the future of the industry.

Be mindful of industry requirements and trends, work within your team to ensure all considerations and assessments are made, and find an effective partner to help in creating these innovative products and bringing them to market.

This article was originally published on EDN.

Kirk Palmer is department manager at Intertek.


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