International Journal of Electrical and Computer Engineering (IJECE) Vol. 10, No. 3, June 2020, pp. 2245~2249 ISSN: 2088-8708, DOI: 10.11591/ijece.v10i3.pp2245-2249  2245 Journal homepage: http://ijece.iaescore.com/index.php/IJECE Wireless power transfer using multiple-transmitters for high stability for position Kazuma Onishi, Kazuya Yamaguchi, Kenichi Iida Department of Control Engineering, National Institute of Technology, Nara College, Japan Article Info ABSTRACT Article history: Received May 24, 2019 Revised Nov 5, 2019 Accepted Nov 24, 2019 The aim of this study is to optimize the system in the wireless power supply using multiple transmitters by algebraically analyzing the effects of both a circuit parameter and an axis displacement, etc. In addition to these analyses, the other aim is designing, producing and evaluating wireless charger with high stability for position. In the proposed method, we analyzed the situation in which three transmitters are used as power sources. It is turned out that the optimum arrangement of three transmitters is equilateral triangular from Biot-Savart law and circuit equation. In the experiment, transmitted power is measured when the receiver is moved on the vertical plane in regard to central axis of coils. It is confirmed that 4~4.5mW is transmitted at the face-to-face of transmitters and 2.4mW is transmitted at the center of transmitters. Keywords: Axial displacement Multiple transmitter Wireless power transfer Copyright © 2020 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Kazuya Yamaguchi, Department of Control Engineering, National Institute of Technology, Nara College, 22 Yata-cho, Yamatokoriyama, Nara, Japan. Email: k-yamaguchi@ctrl.nara-k.ac.jp 1. INTRODUCTION 1Wireless power transfer (WPT) has been studied in various fields such as industry [1, 2], manufacturing [3], medicine [4, 5], and information [6, 7]. The basic principle has been proposed in the 19th century, and since the MIT report in 2007 [8], it has much attracted many researchers. Recently, many papers about WPT have been published, and various products have been examining and commercializing. For example, studies such as examination of design of coils [9-12] and comparison of efficiency by change of applied voltage waveform [13, 14], are investigating. As products, WPT system is applied for power supply on various fields, for instance mobile devices and IoT [15], vehicles traveling on the road [16-19], and micro implant devices [20-22]. As mentioned above, researches finding ideal conditions are actively conducted to improve the performance of WPT [23, 24]. On the other hand, analysis of the situations which degrade performance are not viewed as important, for example leakage flux and misalignment between transmitters and receivers [25, 26]. As a result, there are some restrictions with relation to design of circuits. On the other hand, considering flexibility of the receiver position, the size of the receiving coil depends on the receiving device, and the loss due to leakage magnetic flux etc. occurs remarkably when transmitting coil is too large. Therefore, it is assumed that it is more advantageous to operate WPT circuit by using a few coils than to handle a single large coil in some situations. This paper aims realization of stable power transmission regardless of the position of the receiving coil with using multiple transmitters. In order to utilize multiple transmitters, the electromagnetic interaction between transmitters and receiver must be considered. A calculation method is considered and a mathematical formula based on electromagnetism and circuit theory is expressed so that the user could arbitrarily set parameters such as the number and position of transmitters to improve the versatility. Finally, the experimental verification is performed using the actually designed electric circuit, and it is compared with the theoretical result.