Harmonic injected rotor shape for five-phase surface-mounted permanent magnet machine

Multi-phase machines offer several key features, such as high reliability, high torque density, and high efficiency. Therefore, they are obtained wide applications from automotive to aerospace. One of them is the five-phase PM machine, where the torque density can be improved by injecting third harmonic current . This paper will investigate a five-phase SPM machine with harmonics injected magnets and the amount of increased torque with associated harmonics will also be discussed. Compared to the machine with conventional sinusoidal and sinusoidal with 3rd harmonic shaped PM magnets, the average torque is increased since the space for PM is fully utilized, whilst the torque ripple can be maintained significantly low, resulting in both high torque density and low torque ripple. The FEA predicted back-EMF, cogging torque, torque-current characteristic are validated by experiments on the prototype machines.