Research on Magnetic Field Distribution and Characteristics of a 3.7 kW Wireless Charging System for Electric Vehicles under Offset

Abstract

A 3.7 kW resonant wireless charging system (WCS) is proposed to realize the energy transmission for electric vehicles. In addition to designing the electrical modules functionally, coupling coils are designed and verified by physical prototype, which guarantees the accuracy of coils and subsequent simulations. Then, we focus on the magnetic field distribution of coupling coils in the vehicle environment. Four points (A1, A2, A3, A4) in different regions and three points (the head B1, chest B2 and cushion B3) in the driving seat are helped to measure the magnetic field strength. The magnetic field distribution of coils under five offsets of 60 mm, 120 mm, 180 mm, 240 mm and 300 mm are analyzed theoretically and simulated correspondingly. The simulation results indicate that the magnetic field strength of test points are within the limits, but the strength at A3 is larger than 30.4 A/m required by SAE J2954 at 40% offset and 50% offset. Taking into account the composition of the actual magnetic field, the magnetic field distribution due to side-band and odd harmonic current are also obtained. An experimental bench for the proposed 3.7 kW WCS is built to validate the rightness and feasibility of the simulated scheme. The results of simulation and experiments of magnetic field distribution have less error and are often in good agreement.Energies 2019, 12, 392 3 of 21 obtained separately. In addition, the measurement results of near magnetic field distribution and far magnetic field at the odd frequency of 85 kHz are obtained. An experimental bench for the proposed 3.7 kW WCS is built to validate the rightness and feasibility of the simulation results. Design of the 3.7 kW WCSAccording to regulations on the power of SAE J2954, WPT1 (Wireless Power Transmission level 1) with 3.7 kW WCS is selected as a design product. The overall system is composed as shown in Figure 1. The primary side consists of a grid input, a power factor correction (PFC) circuit, an inverter, a primary compensation topology, and a primary coil, which are arranged on the ground; the secondary side is composed of a secondary coil, a secondary compensation topology, a rectifier, a filter and the battery arranged at the chassis of vehicle. The common part of primary and secondary side is the coupling coils, between which energy is transmitted through a coupling magnetic field.

Safety of Wireless Power Transfer

“…A recent review of reported magnetic fields distributions within or outside the vehicle at several distances and including misalignment conditions [22] suggested that in none of the investigations described in the quoted publications [23][24][25][26][27][28][29], the measured magnetic or electric fields during charging exceeded either the ICNIRP or IEEE exposure limits when proper shielding is involved.…”

Magnetic Field during Wireless Charging in an Electric Vehicle According to Standard SAE J2954

“…For a given WPT class, the magnetic field is maximum for small size vehicles with maximum ground clearance and maximum offset. The goal of this study was to numerically predict the magnetic field in the environment [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. The numerical simulations were carried out by a hybrid technique based on the solution of an electromagnetic (EM) field/circuit coupled problem.…”

Electromagnetic Shielding Techniques in the Wireless Power Transfer System for Charging Inspection Robot Application

“…Passive shielding is a common electromagnetic shielding strategy. Passive shielding refers to the optimization of the magnetic channel by using the magnetic conductivity of magnetic materials or the formation of reverse MF by eddy current produced by conductive metal materials in highfrequency MF, so as to suppress the leakage of MF [4][5][6]. Attaching an aluminum (Al) plate to the transmit (Tx) coil and/or the receive (Rx) coil is the most prevalent measure, which exploits the eddy current induced in the high-conductivity metal to block the leakage field.…”