Abstract
This study applies a multilayer coil technology that can compensate for a decrease in transfer efficiency due to a lateral misalignment in a practical 100 kHz-band wireless power transfer system and validates its effect on the efficiency of compensation. The effectiveness is investigated using coils fabricated with Litz wires. Three-turn rectangular assistant coils 22.4 × 45.3 mm2 in size were stacked on a five-turn circular primary coil with a diameter of 45.3 mm in a 2 × 1 array. Transfer efficiency between two such coils was measured by producing lateral misalignment, while maintaining the vertical distance between the Tx and Rx coils at 7 mm. The experimental results showed that the transfer efficiency was compensated by approximately 46.1%P maximum in a misalignment state of 30 mm, which corresponded to 67% of the maximum size of the coil, compared to the transfer efficiency of the structure, in which the multilayer coil was not applied. Furthermore, transfer efficiency was compensated by 37.6%P, even in an asymmetric system in which the multilayer structure was applied only to the Tx coil, thereby confirming an excellent multilayer coil technology effect on compensation for lateral misalignment in practical cases.
Highlights
Distance-adaptive wireless power transfer systems have been demonstrated based on novel adaptive matching techniques [1,2,3], by over-coupling the coils [4], or by utilizing compensating capacitors [5]
For removing theassistant assistant coil from coil stack. These results shown in Figure comparison, the simulation test results are shown together, and theand results for the convenFor comparison, the simulation test results are shown together, the results for the tional coil pair, which multilayer coil technology was notwas applied at all, are conventional coiltopair, to the which the multilayer coil technology not applied at all, are shown
In the case of a 30 mm misalignment, i.e., a very large misalignment state of 67% compared to the maximum size misalignment, i.e., a very large misalignment state of 67% compared to the maximum size of the coil, the transfer efficiency of the asymmetric system is 58.1%, which is much higher of the coil, the transfer efficiency of the asymmetric system is 58.1%, which is much higher than the 20.8% transfer efficiency of the conventional coil system in the same misalignment than the 20.8% transfer efficiency of the conventional coil system in the same misalignstate
Summary
Distance-adaptive wireless power transfer systems have been demonstrated based on novel adaptive matching techniques [1,2,3], by over-coupling the coils [4], or by utilizing compensating capacitors [5] These methods have demonstrated their potential with an efficiency of as high as 80% for a distance of 50% (relative to the largest coil dimension) between the Tx and Rx coils, the effect is limited to cases where the two coils are well, if not perfectly, aligned. In [6], a transfer efficiency of 80% at a misalignment of 67% relative to the maximum coil dimension was achieved by maximizing the fringing field It requires relatively large coils, which may not be compatible at kHz frequencies.
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