Abstract
Recently, the application of surface-mounted magnet brushless machines to EVs/HEVs is extensively researched. In this paper, the performance of such kind of brushless motor which has a trapezoidal back-emf waveform when operated in BLDC and BLAC modes is evaluated, in both constant torque and flux-weakening regions, assuming (a) the same torque, (b) the same peak current, and (c) the same rms current. It is shown that although the motor has an essentially trapezoidal back-emf waveform, the output power and torque when operated in the BLAC mode in the flux-weakening region are significantly higher than that can be achieved when operated in the BLDC mode due to the influence of the winding inductance and back-emf harmonics.
