Efficiency Improvement of Switched Flux PM Memory Machine Over Interior PM Machine for EV/HEV Applications

Abstract

In this paper, a novel switched flux permanent-magnet (SFPM) memory machine, which consists of changeable magnetized permanent magnets (CMPMs) in the stator, is developed and investigated. By changing the magnetization directions of CMPMs, the PM flux linkage can be either enhanced or weakened. When PM flux linkage is weakened at high speed, the flux density in the lamination as well as iron loss can be reduced. Thus, higher efficiency can be obtained. To evaluate the efficiency improvement of SFPM memory machine, the efficiency map is calculated and compared with that of interior PM machine by taking Toyota/Prius 2010 as benchmark. It shows that several step changes of PM flux linkage can enlarge the high-efficiency region, and also reduce the back-EMF at high speed.