High efficiency dual inverter drives for a PMSM considering field weakening region

This paper describes dual inverter drive for a permanent magnet synchronous motor (PMSM). PMSMs are widely used in many areas including Electric Vehicle (EV). The needs for PMSMs are consistently increasing in spite of its high cost because of its high efficiency. PMSM drive has advantages in low speed because it doesn't need excitation current. But in high speed operation, this characteristic serves as disadvantage and it needs additional currents to reduce the magnetic flux from permanent magnets. This current makes additional losses such as copper loss of the machine and the inverter loss. And these losses cause efficiency drop of the entire drive system. So, it is possible to increase efficiency by making this current low. In this paper, the method which makes lower back-EMF by splitting motor is proposed. By splitting stator, field weakening current is reduced because flux linkage between rotor and stator is reduced. In the split of the machine slots, there are many candidates according to the split ratio. This paper analyzes the efficiency considering both machine and inverter losses simultaneously in the various split. This proposed method is also evaluated by experiments.