Wireless Power Transfer Distance Research Articles

Design and Analysis of Wireless Resolver for Wireless Switched Reluctance Motors

In this article, a wireless resolver is proposed and implemented for wireless switched reluctance (SR) motors, which can detect the rotor position and transfer the information to the primary side without involving any battery storage or active components at the secondary side. The key is to integrate wireless power transfer (WPT) into a variable reluctance resolver to detect and transmit the rotor position. Compared with previous wireless SR motors adopting the Hall effect position encoder and Bluetooth communication, the robustness is highly improved, and the communication delay caused by the connection interval can be solved. Therefore, the proposed system takes the definite advantages of better dynamic performance and sealability. Besides, there is no need to specially design the SR motor, as all existing SR motors and other similar kinds of motors can readily employ this wireless resolver. An experimental prototype has been built for verification, which works well from 100 to 900 rpm with 20 mm WPT distance, and the additional power for position detection can be limited to 1.05 W while the motor consumes 54 W.

Wireless Power Transfer Techniques for Implantable Medical Devices: A Review.

Wireless power transfer (WPT) systems have become increasingly suitable solutions for the electrical powering of advanced multifunctional micro-electronic devices such as those found in current biomedical implants. The design and implementation of high power transfer efficiency WPT systems are, however, challenging. The size of the WPT system, the separation distance between the outside environment and location of the implanted medical device inside the body, the operating frequency and tissue safety due to power dissipation are key parameters to consider in the design of WPT systems. This article provides a systematic review of the wide range of WPT systems that have been investigated over the last two decades to improve overall system performance. The various strategies implemented to transfer wireless power in implantable medical devices (IMDs) were reviewed, which includes capacitive coupling, inductive coupling, magnetic resonance coupling and, more recently, acoustic and optical powering methods. The strengths and limitations of all these techniques are benchmarked against each other and particular emphasis is placed on comparing the implanted receiver size, the WPT distance, power transfer efficiency and tissue safety presented by the resulting systems. Necessary improvements and trends of each WPT techniques are also indicated per specific IMD.

1.06 FoM and Compact Wireless Power Transfer System Using Rectangular Defected Ground Structure Resonators

This letter proposes a wireless power transfer (WPT) system using coplanar waveguide fed rectangular defected ground structure (DGS) resonators. One of the advantages of rectangular DGS resonator is that it has higher quality (Q-) and coupling (K-) factor compared to the H-shape or semi-H-shape DGS resonators. When two DGS resonators are coupled back-to-back, it transforms to a bandpass filter with tight coupling, resulting in the transfer of power wirelessly. The fabricated WPT system of size $35.8~\text {mm} \times 20$ mm achieves, for the first time, a figure of merit of more than one at a WPT distance from 40 to 44 mm.

Analysis and experimental study of wireless power transfer with HTS coil and copper coil as the intermediate resonators system

Intermediate resonator (repeater) between transmitter and receiver can significantly increase the distance of wireless power transfer (WPT) and the efficiency of wireless power transfer. The wireless power transfer via strongly coupled magnetic resonances with an high temperature superconducting (HTS) coil and copper coil as intermediate resonators was presented in this paper. The electromagnetic experiment system under different conditions with different repeating coils were simulated by finite element software. The spatial distribution patterns of magnetic induction intensity at different distances were plotted. In this paper, we examined transfer characteristics with HTS repeating coil and copper repeating coil at 77K and 300K, respectively. Simulation and experimental results show that HTS and copper repeating coil can effectively enhance the space magnetic induction intensity, which has significant effect on improving the transmission efficiency and lengthening transmission distance. We found that the efficiency and the distance of wireless power transfer system with an HTS coil as repeater is much higher by using of copper coil as repeater.

Characteristics analysis on a superconductor resonance coil WPT system according to cooling vessel materials in different distances

The interest in wireless power transfer (WPT) that can send power without using wires has been increasing recently. Especially, there is a great interest in the wireless power devices for portable IT devices. The WPT devices that have been developed so far use the magnetic induction method, and they are not active due to their distance problem. A magnetic resonance WPT method was developed and has been actively researched to resolve this problem. A superconductor coil was applied in this study to increase the efficiency of the magnetic resonance WPT. FRP, bakelite, polystyrene, aluminum, and iron were applied as the cooling vessel material to analyze the WPT distance. The distance between the transmitter and receiver coils started from 800mm and was increased by 200mm. The reflection coefficient was measured at each distance. As a result, FRP, bakelite, plastic PVC, polystyrene of the reflection coefficient was similar. From among these FRP being used for the cooling vessel made the transmission characteristics higher than any other materials when the distance between the transmitter and receiver coils was 2,000mm. On the other hand, the reflection coefficient dropped when iron was used. It is estimated based on the experimental results that the wireless power transmission characteristics and distance of sending power can be improved in the superconductor coil if the cooling vessel is made with FRP.

Indefinite-permeability metamaterial lens with finite size for miniaturized wireless power transfer system

A miniaturized wireless power transfer (WPT) system using indefinite-permeability metamaterial (IPMM) lens with finite size is proposed and investigated theoretically and experimentally. Theoretical simulations show that the IPMM lens outperforms isotropic negative metamaterial (NMM) lens in terms of coupling efficiency and lens size. A highly sub-wavelength IPMM operation at high frequency was designed, fabricated, and measured. The WPT experiments show that the efficiency can be enhanced significantly from 0.7% to 22.0% when the system is loaded with IPMM lens around 4MHz. The further study shows that the IPMM lens can extend the operating distance of WPT by using an optimization approach.

Guest EditorialSpecial Issue on Wireless Power Transfer

Wireless power transfer has been an increasingly attractive topic because it is convenient, clean, and safe. Its applications include industry clean rooms, electric vehicles (EVs), mobile phones, smart pads, medical devices, defense equipment, and robots. The wireless power transfer may mitigate the heavy reliance of a device on the battery that is heavy, expensive, and have a short operating time. The power level of wireless power ranges from a few milliwatts for medical implants and wireless sensors to several hundred kilowatts for EV charging. The distance of wireless power transfer varies from submillimeters to several meters, while the application areas are persistently expanding. Recently, we witness increasing demands for the electrification of public transportation and convenient charging of mobile devices.

A Study on Magnetic Field Repeater in Wireless Power Transfer

It is shown that the distance of wireless power transfer is significantly increased by placing intermediate resonators (repeaters) between transmitter and receiver. The guidelines are provided to use the repeaters effectively. We first briefly review how the repeaters enhance the transfer distance. Next, the aspect of resonant frequency splitting is studied separately both for even and odd numbers of repeaters. The transferred power, efficiency, and output impedance phase are evaluated for each repeater configuration. These provide the guidelines to select the optimum repeater positions and numbers. We also propose and study a new kind of repeater which can be placed (biased) even in the vicinity of transmitter or receiver. This increases the flexibility in choosing the repeater position. The net effect of such biased repeater is approximately doubling the effective coupling coefficient between transmitter and receiver. Experimental results are provided to prove the concepts.