| Summary: | 碩士 === 國立成功大學 === 電機工程學系 === 103 === In this thesis, we investigate the efficiency of inductive wireless power transfer (WTP) systems for electric vehicles in terms of frequency response analysis and the design method. Up to present, most relevant WPT studies were about designing system circuit parameters and designing coupled structures of induction coils. Research on the efficiency of the power conversion from compensation topology composed of induction coils and compensational capacitors is lacking. Study on design methods to increase the efficiency within the operational frequency band range is nonexistent. However, through the equivalent circuit model of compensation topology, this study has derived a conversion efficiency formula for a non-resonant point frequency band in a system. With reference to the inductive charging specification and recommendation in SAE standard J2954 in the frequency band range between 81.38 kHz to 90 kHz, a design process for optimal compensation capacitors was proposed for raising system conversion efficiency, increasing actual operable range, and for system safety consideration. To verify the enhanced method for system conversion efficiency proposed in this article, some collocating peripheral circuits and an inductively coupled contactless energy transfer platform with a 20 cm air gap were used. The experimental data showed that when the operating frequency is 86 kHz, input power is 468.98 W, output power is 434.47 W, and the system power transfer efficiency is 92.64 %. When the operating frequency is adjusted to 90 kHz, the system efficiency increased to 93.65 %. When the operating frequency is 81 kHz, the system efficiency is 91.46 %. This new method is both practical and informative.
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