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Design and Optimization of Litz-Wire Planar Spiral Coil for Inductive Power Transfer Application
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  • Weihao Zhao ,
  • Yingzhou Peng ,
  • Shen Zhan ,
  • Huai Wang
Weihao Zhao
AAU Energy

Corresponding Author:[email protected]

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Yingzhou Peng
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Shen Zhan
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Huai Wang
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Litz wire planar spiral coils are widely used in inductive power transfer systems due to low power loss in high-frequency operation and low profile. However, the complicated structure of the litz wire coil imposes difficulties in estimating the frequency-dependent resistance and quality factor accurately. In this work, we present an 2D analytical model for calculating the frequency-dependent resistance and quality factor of multi-coil inductive power transfer systems based on superposition of different loss effects. Its accuracy is validated with multiple coils and litz wires over wide frequency range. Meanwhile, a fast and accurate multi-objective optimization method is developed to improve the product quality factor and coupling factor. From the optimization results, there are five factors affecting the quality factor and coupling factor. A set of design guidelines is proposed to cope with these design factors. The final prototypes show 33\% increase in quality factor and 23\% improvement in coupling factor compared with the state-of-the-art designs. Meanwhile, a 30W, 500kHz inductive power transfer system is designed with 91\% peak efficiency.