Comparison of electromagnetic performance of 2- and 3-phase PM brushless AC machines for low speed applications

This paper compares the electromagnetic performance, such as average torque, torque ripple, iron loss, and magnet losses, of 2- and 3-phase permanent magnet brushless AC machines for low speed applications, with consideration of different slot/pole number combinations. Each machine is optimized to achieve the maximum torque under the same operation speed and thermal constraints by finite element method. The comparison shows that 2- and 3-phase PM machines have similar torque density and efficiency, although 2-phase machines have significantly larger magnet losses, and higher torque ripple than 3-phase machines for the same pole/slot number combination.