Assessment of Exposure to Electric Vehicle Inductive Power Transfer Systems: Experimental Measurements and Numerical Dosimetry

Abstract

High-power inductive power transfer (IPT) systems for charging light and heavy electric vehicles pose safety concerns if they are installed in uncontrolled environments. Within the framework of the European Project EMPIR-16ENG08 MICEV, a wide experimental and numerical study was conducted to assess the exposure of the general public to IPT stray magnetic fields for two different exposure scenarios: (1) for an IPT model system derived from the SAE J2954 standard operating at 85 kHz for a light electric vehicle coupled with the model of a realistic car-body model; and (2) for an IPT model system with a maximum rated power of 50 kW at 27.8 kHz for a real minibus that was reproduced with some simplifications in two different 3D finite element method (FEM) simulation tools (Opera 3D and CST software). An ad hoc measurement survey was carried out at the minibus charging station to validate the simulations of the real bus station for both aligned and misaligned IPT coils. Based on this preliminary study, a safety factor was chosen to ensure a conservative dosimetric analysis with respect to the model approximations. As highlighted in this study, the vehicle-body serves as an efficient screen to reduce the magnetic field by at least three orders of magnitude close to the coils. By applying FEM, computed spatial distribution to the Sim4Life software, the exposure of three Virtual Population human anatomical phantoms (one adult, one child, and a newborn) was assessed. The three phantoms were placed in different postures and locations for both exposure scenarios. The basic restriction limits, established by the current guidelines, were never exceeded within the vehicles; however, the basic restrictions were exceeded when an adult crouched outside the minibus, i.e., near the coils, or when a newborn was placed in the same location. Borderline values were observed in the light car. In the case of the bus, limits coming from the Institute of Electrical and Electronics Engineers (IEEE) guidelines are never exceeded, while basic restrictions coming from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines are exceeded up to 12% for an adult and up to 38% for a newborn. This paper presents novel dosimetric data generated in an IPT system for heavy vehicles and confirms some of the literature data on light vehicles.

A Measurement System for the Characterization of Wireless Charging Stations for Electric Vehicles

“…The scheme and more details on the MU are reported in [15], together with the measurement uncertainty assessment and an example of application in two charging stations. In this article, we will mainly focus on the other two units, BU and GU.…”

“…Relative discrepancies tested in the laboratory are lower than 0.02%. The MU accuracy and traceability are discussed in [15].…”

“…Such a level of uncertainty should be sufficient to verify existing on-site measurement systems that, according to common regulations (e.g., ANSI C12.20), should be in class 0.2 or 0.5. For what concerns magnetic measurements, detailed analysis and measurement examples are reported in [15].…”

Real-Time Numerical Dosimetry of Low-Frequency Electromagnetic Fields by Using Multipoles

“…WCS of electrical vehicles is a promising technology. The issue of involuntary exposure to stray fields generated by WCS systems is a hot topic which is being actively investigated [12], [15], [16], [17]. We simulated the exposure of an adult close to a WCS coil, which is representative of existing devices.…”

Assessment of the Overall Efficiency in WPT Stations for Electric Vehicles

“…The measurements at the resonant circuit are interesting with regard to evaluating the actual power transferred to the vehicle, net of losses in the converters. Moreover, the measurements of the coil currents are indirectly useful for the dosimetric evaluation of human exposure to the magnetic fields produced by resonant coils [27]. In this section we discuss a reasonable uncertainty target for these measurements, which arises from the analysis of the waveforms measured on-site.…”