非正弦供电十五相感应电机气隙磁势分析

根据非正弦供电十五相感应电机不同次谐波电流可以产生同速气隙磁势的特点，说明利用3次谐波磁势降低基波磁势幅值以改善电机性能指标的理论根据，并确定叠加磁势峰值达到最小时的3次谐波激磁电流表达式。对感应电机中的非正弦电流进行傅里叶分解，通过计算各次谐波电流产生的不同次谐波磁势，揭示了谐波电流产生同次谐波磁势时、其转速为同步速之规律。以叠加磁势数学表达式为基础，通过求导计算叠加磁势峰值，再由优化方法中的直接法确定出叠加磁势最小峰值以及相应3次谐波激磁电流有效值和相位角。分析了磁势峰值降低后电机性能指标改善及功率密度提高的原因，为十五相感应电机优化提供了理论基础。

Air-gap MMF Analysis of Fifteen-phase Induction Motor With Non-sinusoidal Supply

The magneto-motive forces (MMFs) resulting from the different order harmonic currents of fifteen-phase induction motor under the non-sinusoidal supply may be of the same rotating speeds, which shows that 3-order harmonic MMF can be utilized to decrease the amplitude of the fundamental MMF and improve the performance indexes of the machine. 3-order harmonic exciting current is also obtained for minimizing the amplitude of the superposed MMF. By Fourier analysis, the non-sinusoidal current of the induction motor is resolved into fundamental component and a series of harmonic components, from which the resulted space MMFs are calculated. The fact that the harmonic MMF from the same order harmonic current rotates at the synchronous speed is discovered. Based on the mathematical expression for the superposed MMF, the amplitude of it is achieved by means of the derivation. The direct search method is performed to yield the minimum amplitude, thus also determining the effective value and phase angle of the corresponding 3-order harmonic exciting current. The reasons that the performance indexes of the machine are improved and the power density is increased are presented, which provides the theoretical foundation for optimization design of fifteen-phase induction motors.