Comparison of Electromagnetic Properties Between Hybrid Rotor and Spoke-Type Rotor of PM Machines

This paper presents models of two types of permanent magnet (PM) mahines which called hybrid rotor mahcine and spoke-type rotor mahcine. These two types of mahcines have different significant advantages in output performance under different operating conditions. For revealing the influence of pole numbers and rotor sizes on the performance between the hybrid rotor and spoke-type rotor of PM machines, this paper reserch on the torque profile, air-gap magnetic density, back electromotive force (back-EMF) and eddy loss have been investigated, and the influence of reluctance torque on output was analyzed. The results indicate that the sinusoidal characterisitic of radial magenetic flux density and back-EMF of hybrid rotor machine is better and the loss is less under the large pole numbers and small size operation condition. The comparison results also show that the hybrid rotor PM machine has higher torque density and lower ripple under small rotor size and less pole nmubers operation condition, which is caused by the flux-focusing effect of surface mounted PM. However, in the case of large rotor sizes, hybrid rotor PM machine do not have advantage in average torque, but ripple is still relatively low.