Current waveforms for high torque to current ratio in surface mounted permanent magnet synchronous motors

In this paper, a new magnet configuration is proposed to get high torque to current ratio in the surface mounted PM motors. However, with increase of the output torque, the electromotive force (EMF) waveform in the proposed magnet configuration (segmented ring type) will greatly distort and change from sinusoidal to trapezoidal. This is one of the important reasons for inducing pulsation in the output torque. To eliminate the ripple of the output torque of the motor, it is necessary to supply a nonsinusoidal phase current to compensate the nonsinusoidal EMF. This paper describes an approach to feed the nonsinusoidal phase current to an experimental motor for eliminating the pulsation of the output torque by the three-phase full-bridge inverter circuit without zero-phase-sequence current.