Search

Current wireless power transfer (WPT) systems have limited charging distance and high induced electromagnetic field (EMF) leakage. Thus, we first proposed a thin printed circuit board (PCB) type hybrid metamaterial slab (HMS) combining two kinds of metamaterial cell structures. The metamaterial cells in the center area of the HMS have zero relative permeability and straighten the magnetic field direction. The metamaterial cells located at the edges of the HMS have negative relative permeability and change the outgoing magnetic fields to opposite direction by magnetic boundary condition. Therefore, the magnetic field can be more confined between transmitter and receiver coils, enhancing the power transfer efficiency, while decreasing the EMF leakage in a WPT system. In this paper, we demonstrated that increased power transfer efficiency from 34.5% to 41.7% and reduced EMF leakage from −19.21 to −26.03 dBm in 6.78-MHz WPT system. Furthermore, we proposed new analysis method for relative permeability measurement of the metamaterial using a novel cubic structure with perfect electrical conductor and perfect magnetic conductor boundary. [ABSTRACT FROM PUBLISHER]

Wireless power transfer (WPT) technology is an electrically safe and convenient method of charging batteries. WPT technology allows elimination of exposed contacts, which can cause direct electrocution of human. In spite of the great advantages, the WPT system inevitably generates strong electromagnetic fields (EMFs), causing interference on the nearby electrical devices as well as harmful influence on human health. Therefore, it is important to satisfy EMF guidelines and reduce leakage magnetic field harmonics in WPT system. For the first time, in this paper, we propose a new tightly coupled handheld resonant magnetic field (HH-RMF) charger operating at 20 kHz with low EMF and high efficiency. Using a guided magnetic flux in resonance structure, 64.5 mG of EMF is reduced compared to the conventional inductive charger at a distance of 200 mm from edge of the core. In addition to the electromagnetic interference (EMI) reduction, the isolation inductor scheme is proposed as an EMI reduction method. Through a series of measurements, we experimentally verified that the proposed HH-RMF charger complies with the regulations published by the International Commission on Non-Ionizing Radiation Protection in 1998. The proposed HH-RMF charger with the isolation inductor scheme successfully reduces the third harmonic of the Tx and Rx currents by 23.4 and 11.8 dBμA, respectively. Furthermore, the third and fifth magnetic field harmonics reduce by 1.38 and 0.67 mG, respectively. The coil-to-coil power transfer efficiency and total system power transfer efficiency of the proposed structure are maintained at over 98% and 84%, respectively. [ABSTRACT FROM AUTHOR]

Current wireless power transfer (WPT) technology can only allow power transfer over a limited distance because, as the distance between the transmitter (Tx) and receiver (Rx) coils increases, the power transfer efficiency (PTE) decreases with a steep slope, while the electromagnetic field (EMF) leakage increases. In order to increase the PTE and decrease the EMF leakage simultaneously, we need to develop a method to concentrate the magnetic fields between the Tx and Rx coils. In this paper, we proposed a novel metamaterial structure to realize high efficiency and low EMF leakage. Metamaterials can confine the magnetic fields between the Tx and Rx coils by negative relative permeability. We designed and fabricated a thin metamaterial using a 1.6-mm dual layer printed circuit board (PCB) with a high dielectric constant substrate and a fine pattern to achieve a negative relative permeability with low loss at 6.78 MHz. The thin PCB-type metamaterial has a wide range of applications with low fabrication cost, light weight, and a simple fabrication process. We demonstrated a 44.2% improvement in the PTE and 3.49-dBm reduction in the EMF leakage around the WPT system at 20-cm distance. Furthermore, we first analyzed metamaterials from an EMF point of view using the 3-D magnetic field scanner. Finally, we discussed a combination of metamaterials and ferrites to further improve the PTE and reduce the EMF leakage for long-distance mobile WPT systems. [ABSTRACT FROM PUBLISHER]

Wireless charging of electric vehicles based on wireless power transfer (WPT) has become increasingly popular in recent years. However, a leakage electromagnetic field (EMF) that affects other electronic devices or the human body is inevitably generated from the coils of a WPT system, and requirements regarding the suppression of the leakage EMF are increasing. In this paper, we propose a novel three-phase power line in a WPT system for the reduction of the leakage EMF. The proposed structure employs six power lines to reduce the leakage magnetic flux. This structure is compared with conventional power line structures with respect to induced voltage and magnetic field distribution. We also present analytical solutions of the EMF for the proposed and conventional power line structures. These solutions are then compared with numerical solutions using 3-D finite-element analysis and good agreement is demonstrated. The results of the numerical analysis indicate that the proposed power line can significantly reduce the leakage magnetic field from a WPT system. For verification, the proposed and conventional power lines are implemented and the EMFs are measured. A strong correlation between the numerical and experimental results is exhibited. [ABSTRACT FROM PUBLISHER]