Testing and Assessment of EMFs and Touch Currents From 25-kW IPT System for Medium-Duty EVs

• Published in: IEEE transactions on vehicular technology 2019-08, Vol.68 (8), p.7477-7487
• Main Authors: Mohamed, Ahmed A. S., Meintz, Andrew, Schrafel, Peter, Calabro, Anthony
• Format: Article
• Language: English
• Subjects: ADVANCED PROPULSION SYSTEMS; Automotive parts; Current measurement; Electric contacts; Electric vehicle charging; electric vehicles; Electric vehicles (EV); Electromagnetic fields; electromagnetic fields (EMFs); Electronic devices; Guidelines; human exposure; inductive power transfer; inductive power transfer (IPT); Inspection; Measuring instruments; Metals; Power supplies; Power transfer; Safety; Technology transfer; Touch; touch current; Transmitters; Vehicle dynamics; Wireless communication
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2019.2920827

Inductive power transfer technology has gained massive attention for electric vehicle charging due to the associated reliability, convenience, and safety. Nevertheless, the loose coupling between the transmitter and receiver generates intensive electromagnetic fields (EMFs) around the system, which may influence living objects' safety if the typical limits are exceeded. Moreover, these fields induce voltages in the vehicle body, which may lead to touch current passing through the human body when it gets in contact with two metal parts or one part and the ground. Following the international standards and recommendations, this paper presents comprehensive test guidelines for the near-EMFs and touch currents from a commercial 25-kW wireless charger from Momentum Dynamics, which was installed in an electric shuttle operating at the National Renewable Energy Laboratory (NREL) campus. The paper investigates the measuring devices, test setup, test points, and standard limits. The impact of the misalignments on the measurements is considered during testing. EMFs are measured in areas around and inside the shuttle and near the power supply and compared with the reference levels defined by the international standards, including ICNIRP 2010, IEEE C95.1, and ACGIH TLV 2017. Touch currents are evaluated among different metal parts and ground in comparison with the standard limits. The results show that both EMFs and touch currents comply with the standard limits. Moreover, thermal inspection for the system after installation was provided. Finally, five days of operation data for the wireless charger are collected and presented.