An innovative PM motor with phases series connection devoted to EV drives

Current-regulated PWM voltage-source inverters with either sinusoidal or square-wave output are the most common power electronic converters used to feed PM motors. Square-wave fed permanent magnet motors yield a higher torque whereas the torque ripple of sine-wave fed brushless motors is significantly lower. An innovative topology of dc brushless motor with the stator phases being fed in series by means of a solid-state-commutator (SSC) is presented in this paper. The solid-state-commutator provides each motor phase with 180° square wave current timed with respective emf. With a PM motor having 60° flat-top trapezoidal-wave emf, the proposed novel configuration results in no torque ripple and higher average torque compared to conventional brushless dc motor drives with 120° square-wave current supply. The proposed drive arrangement is suitable for EV propulsion systems based on the use of wheel motors. The paper discusses the principle of operation of the proposed drive arrangement and shows experimental waveforms taken from a drive prototype.