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.

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 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.

With advancements in the field of electrical engineering, various low-power portable electronic devices have been commercialized. To eliminate and unify different types of cables, inductive wireless power transfer (WPT) technology, which uses magnetic fields to transfer energy, is being applied in numerous applications. Low-power devices typically have small coils and loads, leading to low power transfer efficiency even over short distances. Magnetic materials such as ferrites are used to improve power transfer efficiency (PTE). It is well known that high-permeability ferrites with low magnetic reluctance are ideal for achieving strong magnetic coupling. However, continuous increases in permeability raise the cost and weight of the ferrite, making it necessary to select ferrites with appropriate permeability from a mass-production perspective. This paper models and analyzes the changes in mutual inductance and power transfer efficiency with varying ferrite permeabilities using magnetic circuits, providing guidelines for the selection of suitable ferrites considering efficiency improvements. The proposed method is validated through 3D electromagnetic simulations and experiments, showing a power transfer efficiency difference of up to 0.6% between the experimental and calculated results.

In this article, we propose a method for deembedding the effects of mounting pads and via-holes in test fixture for accurate impedance measurement of the passive component of surface mount devices (SMDs). Impedance of the SMD passive component is measured mounted on the test fixture because it cannot be probed directly. Hence, the measurement results include the effects of the test fixture. Deembedding is required to extract the impedance of the device under test alone. Existing deembedding methods such as short-open-load-thru (SOLT), thru-reflect-line (TRL), and 2x thru deembedding cannot eliminate the effects of the mounting pads and via-holes of the test fixture, leading to large measurement errors. Our proposed method can extract the parasitic components of the mounting pads and via-hole using open and short fixtures, and then deembed the mounting pads and via-hole. Furthermore, two guidelines for designing the short and open fixtures are proposed. We validated our proposed method through a simulation and measurement. From the measurement result of the multilayer ceramic capacitors, the difference in the equivalent series inductance (ESL) between the 2x thru deembedding method and the proposed method was analyzed. Additionally, we confirmed that the self-impedance and SSN voltage of the power distribution network (PDN) had larger value due to the ESL error. By reducing the ESL error, the SSN voltage was decreased by about 5%, thus saving the number of decoupling capacitors.