A wireless power transfer system for multi-user charging is proposed to demonstrate a robust quasi-uniform power efficiency in a 3-D space. It employs a set of balanced magnetic coils excited with phase-shifted currents on the transmitting side to feature omnidirectionality. In this article, two transmitter structures, 2-coil and 3-coil systems are discussed and compared. These systems produce a quasi-uniform magnetic field magnitude regardless of the locations of the receiving coils provided that the coils point to the center of the transmitting system sphere at the same distance. A simulation platform is established for the proposed method. Experimental results at 2MHz substantiate a uniform spatial efficiency and bound the average error of analytical calculations within 10%. Furthermore, the proposed method with rotating fields based on phase-shifted currents shows that the 3-coil system yields a higher efficiency and a lower efficiency spread, 6.8% improvement on average efficiency and 88.7% reduction on efficiency variance, compared to the 2-coil system.

中文翻译：

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基于旋转场的鲁棒3D无线电力传输系统，可为多用户充电

提出了一种用于多用户充电的无线电力传输系统，以证明在3-D空间中鲁棒的准均匀功率效率。它在发射侧采用了一组由相移电流激励的平衡电磁线圈，具有全向性。在本文中，讨论并比较了两种变送器结构，即2线圈和3线圈系统。这些系统将产生准均匀的磁场强度，而与接收线圈的位置无关，只要这些线圈指向发射系统球体的中心的距离相同即可。针对该方法建立了仿真平台。2MHz的实验结果证实了均匀的空间效率，并将分析计算的平均误差限制在10％以内。此外，