Design Of High Power Density Permanent Magnet Machine And Analysis Of Mitigation Method Of Short Circuit Current

Due to its high power density and high efficiency,the Permanent Magnet Synchronous Machine(PMSM)has been attracting increasingly attention in the aircraft power system and the electric vehicle.However,the turn-to-turn short circuit current of the permanent magnet manchine is large,and cannot be mitigated easily,which restricts its application in the area where high reliability matters,such as aircraft starter generator systems.The higher reliability always leads to lower power density.The method of mitigating the turn-to-turn short circuit current while maintaining its high power density is of great importance.In this study,the mitigation methods of the turn-to-turn SC current are analyzed and compared.The designing method of high-reliability,high-power-density PMSM is preliminarily summarized.In this study,the basic operating principle and structure of permanent magnet motor are firstly analysed.The influence of the bridge of the spoke type permanent magnet machine on the basic electromagnetic performance is studied.Based on the 12-slot,10-pole fractional slot concentrated windings(FSCW)permanent magnet machine,the basic characteristic of the turn-to-turn short circuit current is analyzed.The worst case of turn-to-turn short circuit fault is deduced.The influence of turn-to-turn short circuit current on electromagnetic performance and temperature distribution of the machine is analyzed.It provides theoretical support for the detection and mitigation of the turn-to-turn fault.The influence of the basic structural parameters of the machine on the short circuit current and output power is studied,which provides a theoretical basis for the design method of high-power-density and high-reliability permanent magnet motor.The mitigation methods,i.e.,shorting three phase terminal,shorting faulty phase terminal,three phase flux-weakening current injection and faulty phase flux-weakening current injection,are compared and analysed.The design criteria for high-power-density and high-reliability PMSM are preliminarily derived.The prototype and experiment platform are built.The basic electromagnetic characteristics of the prototype and short circuit characteristics are tested.The effectiveness of the three phase flux-weakening current injection method is verified by experiments.