Electromagnetic performance of surface-mounted permanent magnet machines with third harmonic injected rotor and overlapping winding

This paper compares the electromagnetic performance of three phase 24-slot/8-pole surface-mounted permanent magnet (SPM) machines with various permanent magnet shapes, in which the overlapping winding is employed. The permanent magnets (PM) on the rotor are designated as conventional one, sine shape, and sine shape with third harmonic injection. It is found that compared with machines with Sine-shaped PMs, the average torque of machines with Sine+3rd-shaped PMs can be improved by>9% but the cogging torque increases. The increased cogging torque can be reduced by optimizing the configurations of machines such as the width of slots, yoke and teeth. The third harmonic in the airgap flux density is introduced by the PM rotor of sine shape with third harmonic injection, and thus the iron losses are also compared among the machines with different PM shapes.