Wireless power transfer (WPT) systems use a magnetic field as the medium for transferring power wirelessly. During the transfer process, there are two magnetic fields, which are called the coupling magnetic field and the leakage magnetic field. The leakage magnetic field can cause electromagnetic field (EMF) and electromagnetic interference (EMI) issues. In WPT systems, when transferring power from source to load, EMF can affect humans due to the strong magnetic field. EMI can cause interference with other electronic devices due to the harmonic magnetic field. Before a WPT system can be commercialized, the EMF and EMI issues must both be solved. Additionally, EMF and EMI regulations must be met. This article proposes a method of designing resonant circuit components to suppress EMF and EMI in WPT systems for electric vehicles (EVs). The processes of suppressing EMF and EMI are explained. The proposed method was verified through simulation and experiment. Results showed that EMF can be suppressed by up to 50%, and EMI can be suppressed by up to 14 dB.

In this paper, we propose a method to reduce the leakage magnetic field from wireless power transfer (WPT) systems with series–series compensation topology by adjusting the phase difference between the transmitter (TX) coil current and the receiver (RX) coil current without additional shielding coils or materials. A WPT system employing the proposed method adjusts the phase difference between the TX coil current and RX coil current by tuning a resonant capacitor of the RX coil. The conditions for minimizing the leakage magnetic field are derived, and the range of the resonant capacitor of RX, considering power transfer efficiency and the leakage magnetic field, is proposed. Through simulations and experiments, it is verified that the proposed method can reduce the leakage magnetic field level without any additional materials. For that reason, the proposed method can be suitable for size-limited, weight-limited or cost-limited WPT systems.

This paper analyzes how over-coupled coils affect odd harmonic current and electromagnetic interference (EMI) in a wireless power transfer (WPT) system, and proposes design considerations for series inductors to solve the EMI problem. When the air gap of the coils of the WPT system decreases below a certain level and the coils are over-coupled, the odd harmonic component of the input impedance of the system decreases and odd harmonic currents increase. The increase in the odd harmonic components current quickly aggravates the EMI issues. To solve the EMI problem of the over-coupled WPT system, additional series inductors were applied to the system, and considerations for designing the series inductors were analyzed. When designing additional series inductors, power transfer efficiency, maximum power transfer, input impedance and odd harmonic components current must be considered. Using simulations and experiments, it was confirmed that the WPT system designed with analyzed considerations maintained relatively high efficiency and reduced EMI issues.

In this paper, we propose a method of wirelessly torque transfer (WTT) and power (WPT) to a drug pump, one of implantable medical devices. By using the magnetic field generated by the WPT system to transfer torque and power to the receiving coil at the same time, applications that previously used power from the battery can be operated without a battery. The proposed method uses a receiving coil with magnetic material as a motor, and can generate torque in a desired direction using the magnetic field from the transmitting coil. The WPT system was analyzed using a topology that generates a constant current for stable torque generation. In addition, a method for detecting the position of the receiving coil without using additional power was proposed. Through simulations and experiments, it was confirmed that WTT and WPT were possible at the same time, and in particular, it was confirmed that WTT was stably possible.

This paper proposes a shielding sensor (SS) coil to solve the misalignment issue and the leakage magnetic field issue of the wireless power transfer (WPT) system for electric vehicles (EVs). The misalignment issue and leakage magnetic field issue must be solved because they can cause problems with power transfer efficiency reduction and electronic device malfunction. To solve these problems, the proposed SS coils are located over the Tx coil. The newly created mutual inductance between the Tx coil and the SS coil is used to detect the misalignment of the receiver in the Tx coil. In addition, the current phase of the SS coil is adjusted through impedance control of the SS coil to reduce the leakage magnetic field. The proposed SS coils were applied to the standard SAE J2954 model for the wireless charging of an EV. The WPT3/Z2 model of SAE J2954 with output power of 10 kW was simulated to compare the shielding effect according to the power transfer efficiency, and it was confirmed that a shielding effect of 76% was shown under the condition of a 3% reduction in the power transfer efficiency. In addition, the occurrence and direction of the misalignment between the receiver and the Tx coil were confirmed by using the tendency of mutual inductance between each SS coil and the Tx coil. In addition, as in the simulation result, the shielding effect and tendency were confirmed in an experiment conducted with the output power downscaled to 500 W.

This letter proposes a method for selectively reducing harmonic magnetic field. When a wireless power transfer (WPT) system transmits power using a magnetic field as a medium, a leakage magnetic field inevitably occurs nearby. Meanwhile, a square wave voltage is generated by high-frequency switching of the inverter or rectifier used in the WPT system, and this square wave voltage is divided into fundamental and harmonic components. Harmonic components are radiated through the coil and can cause interference in other electronic devices, resulting in an electromagnetic interference (EMI) problem. The proposed method selectively and completely reduces harmonics by modifying the double-sided LCC topology. The approach was verified through an experiment, showing that the third harmonic and fifth harmonic can be reduced by 16.03 and 18.27 dB, respectively.