scholarly journals Reduction in Human Interaction with Magnetic Resonant Coupling WPT Systems with Grounded Loop

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7253
Author(s):  
Xianyi Duan ◽  
Junqing Lan ◽  
Yinliang Diao ◽  
Jose Gomez-Tames ◽  
Hiroshi Hirayama ◽  
...  
Keyword(s):  
Electric Field ◽  
Human Body ◽  
High Efficiency ◽  
Transmission Efficiency ◽  
Human Interaction ◽  
Whole Body ◽  
Maximum Efficiency ◽  
Spatial Average ◽  
Power Transfer ◽  
Resonant Coupling

Wireless power transfer (WPT) systems have attracted considerable attention in relation to providing a reliable and convenient power supply. Among the challenges in this area are maintaining the performance of the WPT system with the presence of a human body and minimizing the induced physical quantities in the human body. This study proposes a magnetic resonant coupling WPT (MRC-WPT) system that utilizes a resonator with a grounded loop to mitigate its interaction with a human body and achieve a high-efficiency power transfer at a short range. Our proposed system is based on a grounded loop to reduce the leakage of the electric field, resulting in less interaction with the human body. As a result, a transmission efficiency higher than 70% is achieved at a transmission distance of approximately 25 cm. Under the maximum-efficiency conditions of the WPT system, the use of a resonator with a grounded loop reduces the induced electric field, the peak spatial-average specific absorption rate (psSAR), and the whole-body averaged SAR by 43.6%, 69.7%, and 65.6%, respectively. The maximum permissible input power values for the proposed WPT systems are 40 and 33.5 kW, as prescribed in the International Commission of Non-Ionizing Radiation Protection (ICNIRP) guidelines to comply with the limits for local and whole-body average SAR.

scholarly journals Reduction of Human Interaction with Wireless Power Transfer System Using Shielded Loop Coil

Electronics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 953
Author(s):  
Akihiko Kumazawa ◽  
Yinliang Diao ◽  
Akimasa Hirata ◽  
Hiroshi Hirayama
Keyword(s):  
Equivalent Circuit ◽  
Human Body ◽  
Impedance Matching ◽  
Wireless Power Transfer ◽  
Transmission Efficiency ◽  
Human Interaction ◽  
Power Transfer ◽  
Wireless Power ◽  
Equivalent Circuit Analysis ◽  
Loop Coil

The impedance variation of wireless power transfer (WPT) coils owing to the presence of the human body may result in mismatches, resulting in a decrease of the transmission efficiency. In addition, one of the decisive factors of the permissible transfer power in WPT systems is a compliance assessment with the guidelines/standards for human protection from electromagnetic fields. In our previous study, we reported that a shielded loop coil can potentially reduce human interaction with WPT coils. In this study, first, the rationale for this reduction is investigated with equivalent circuit models for a WPT system using a shielded loop coil operated in close proximity to the human body. We then conducted an equivalent circuit analysis considering the capacitance between the inner and outer conductors of the shielded loop coil, suggesting the stability of the impedance matching. From computational results, the mitigation capability of the shielded loop coil on impedance matching and transmission efficiency owing to the presence of the human body was verified for 6.78 MHz wireless power transfer. Additionally, the reduction of the specific absorption rate (SAR) with coils comprised of the shielded loop structure was confirmed in the presence of anatomically realistic human body models. The maximum transferable power was increased from 1.5 kW to 2.1 kW for the restrictions of the local SAR limit prescribed in the international safety guidelines/standard.

scholarly journals Highly Efficient Target Power Control for Two-Receiver Wireless Power Transfer Systems

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2726 ◽  
Author(s):  
Weikun Cai ◽  
Dianguang Ma ◽  
Houjun Tang ◽  
Xiaoyang Lai ◽  
Xin Liu ◽  
...  
Keyword(s):  
Output Power ◽  
High Efficiency ◽  
Impedance Matching ◽  
Wireless Power Transfer ◽  
Mutual Inductance ◽  
Maximum Efficiency ◽  
Power Transfer ◽  
Wireless Power ◽  
Target Power ◽  
Target Output

Multiple-receiver wireless power transfer (MRWPT) systems have revolutionary potential for use in applications that require transmitting power to multiple devices simultaneously. In most MRWPT systems, impedance matching is adopted to provide maximum efficiency. However, for most MRWPT systems, achieving target power levels and maximal efficiency is difficult because the target output power and maximum efficiency conditions are mostly not satisfied. This study establishes a target power control (TPC) strategy to balance providing target transfer powers and operating under high efficiency. This study is divided into the following points: First, this study derives the optimal mutual inductance to verify that it’s difficult for two-receiver wireless power transfer (WPT) system to achieve both maximum efficiency and power distribution simultaneously; Second, this study illustrates that for impedance matching method the mutual inductances play a more important role than equivalent impedances in increasing the system efficiency, and hence system should give priority in improving the mutual inductance as large as possible; Third, this study proposes a simplified system model which helps to derive the analytic solutions of equivalent impedances; Fourth, this study developed a 100-kHz two-receiver WPT system and establishes a TPC strategy for enabling the system to achieve target output power levels with high efficiency; At last, the proposed system is proved to achieve an efficiency level of more than 90 % and satisfies the target output power levels requirements.

scholarly journals A Consideration on Maximum Efficiency of Resonant Circuit of Inductive Power Transfer System with Soft-Switching Operation

2019 ◽  
Vol 10 (3) ◽  
pp. 54 ◽  
Author(s):  
Ryosuke Ota ◽  
Dannisworo Sudarmo Nugroho ◽  
Nobukazu Hoshi
Keyword(s):  
High Efficiency ◽  
Soft Switching ◽  
Maximum Efficiency ◽  
Resonant Circuit ◽  
Power Transfer ◽  
Switching Operation ◽  
Inductive Power Transfer ◽  
Battery Chargers ◽  
Secondary Side ◽  
Inductive Power

By using bi-directional inductive power transfer (IPT) systems as battery chargers for electric vehicles (EVs), battery charging operations become convenient and safe. However, IPT systems have problems such as occurrences of much electromagnetic noise and power loss because the converters of IPT systems are driven in high frequency by tens of kHz. To solve these problems, there is a case where the soft-switching technique needs to be applied to the converters of IPT systems. However, in soft-switching operation, the power factor of the resonant circuit becomes lower, resulting in a lower resonant circuit efficiency. In previous works, when the soft-switching technique was applied to the converters, the resonant circuit had not always been able to be operated with high efficiency because the influence caused by soft-switching operation had not been considered. For this reason, there was a case where the efficiency of the overall system with soft-switching operation became lower than the efficiency in hard-switching operation. Therefore, in this paper, the influence on the efficiency of the resonant circuit caused by the soft-switching operation is clarified by the theoretical analysis and experiments; then, the guideline for improving the efficiency of IPT systems is shown. As a result, in the experiments, it could be understood that the efficiency of the overall system with soft-switching operation becomes higher than the efficiency in hard-switching operation when the operating point of the resonant circuit was close to the requirement guideline, which is shown by using the primary-side voltage and the secondary-side voltage of the resonant circuit. Therefore, it is suggested that the efficiency of IPT systems could be improved by properly regulating the primary-side direct current (DC) voltage.

A Solution to Frequency Splitting in Magnetic Resonance Wireless Power Transfer Systems Using Double Sided Symmetric Capacitors

2021 ◽  
Vol 5 (2) ◽  
pp. 6-12
Author(s):  
Thabat Thabet ◽  
John Woods
Keyword(s):  
Magnetic Resonance ◽  
Resonance Frequency ◽  
High Efficiency ◽  
Impedance Matching ◽  
Wireless Power Transfer ◽  
Maximum Efficiency ◽  
Power Transfer ◽  
Wireless Power ◽  
Frequency Tracking ◽  
Tuning Method

The technology of wireless power transfer using magnetic resonance coupling has become a subject of interest for researchers with the proliferation of mobile. The maximum efficiency is achieved at a specific gap between the resonators in the system. However, the resonance frequency splits as the gap declines or gets smaller. Different methods have been studied to improve this such as frequency tracking and impedance matching, including capacitive tuning. However, the system has to maintain the same working frequency to avoid moving out of the license exempt industrial, scientific, and medical (ISM) band; and the efficiency must be as large as possible. In this paper, a symmetric capacitance tuning method is presented to achieve these two conditions and solve the splitting problem. In the proposed method, the maximum efficiency at one of the splitting frequencies is moved to match the original resonance frequency. By comparison to other works, both simulation and experiment show considerable improvements for the proposed method over existing frequency tracking and impedance matching methods. The paper also presents a proposal to apply this method automatically which can achieve wireless charging for electronic applications with high efficiency and through variable distance.

scholarly journals Optimal Solutions for Underwater Capacitive Power Transfer

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8233
Author(s):  
Hussein Mahdi ◽  
Bjarte Hoff ◽  
Trond Østrem
Keyword(s):  
High Efficiency ◽  
Autonomous Underwater Vehicles ◽  
Low Frequency ◽  
Underwater Vehicles ◽  
Separation Distance ◽  
Maximum Power ◽  
Capacitive Coupling ◽  
Maximum Efficiency ◽  
Power Transfer ◽  
Coupling Parameters

Capacitive power transfer (CPT) has attracted attention for on-road electric vehicles, autonomous underwater vehicles, and electric ships charging applications. High power transfer capability and high efficiency are the main requirements of a CPT system. This paper proposes three possible solutions to achieve maximum efficiency, maximum power, or conjugate-matching. Each solution expresses the available load power and the efficiency of the CPT system as functions of capacitive coupling parameters and derives the required admittance of the load and the source. The experimental results demonstrated that the available power and the efficiency decrease by the increasing of the frequency from 300 kHz to 1 MHz and the separation distance change from 100 to 300 mm. The maximum efficiency solution gives 83% at 300 kHz and a distance of 100 mm, while the maximum power solution gives the maximum normalized power of 0.994 at the same frequency and distance. The CPT system can provide a good solution to charge electric ships and underwater vehicles over a wide separation distance and low-frequency ranges.

scholarly journals Small-Size Wearable High-Efficiency TAG Antenna for UHF RFID of People

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Milan Svanda ◽  
Milan Polivka
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Human Body ◽  
High Efficiency ◽  
Electric Field Distribution ◽  
Relative Size ◽  
Total Efficiency ◽  
Uhf Rfid ◽  
Low Profile ◽  
Better Than

This paper introduces a small-size, low-profile wearable radiator based on the coupled patches and vertically folded patches techniques for application as a tag antenna for identification of people in the European UHF RFID band. The electric field distribution comes out dominantly from the central coupling slot, and thus the electric properties of the radiator are almost unaffected by the human body to which the antenna is intended to be attached. Accordingly, with the relative size0.14×0.12×0.009 λ0at 866 MHz(50×40×3.04 mm3), the antenna exhibits total efficiency better than 50%, even if it is attached directly to a person.

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