A Novel Asymmetric Interior Permanent Magnet Synchronous Machine

In this paper, a novel asymmetric interior permanent magnet (AIPM) synchronous machine is proposed. Its asymmetric rotor topology, designated as 1.5-layer permanent magnet (PM) structure, features an asymmetric arrangement of the V-shape PMs and the spoke PMs, together with an asymmetric flux barrier located near the rotor surface in each pole. They are employed to utilize the magnetic-field-shifting (MFS) effect for torque enhancement by reducing the current angle difference between peak PM and reluctance torque components. Effects of geometric parameters of the 1.5-layer rotor design, namely asymmetry and pole arc of V-shape cavity as well as position and dimensions of flux barrier, on maximum torque and air-gap field are investigated. Three machines, i.e. the proposed 1.5-layer AIPM, a 1.5-layer symmetrical rotor topology IPM-I and a conventional single layer V-shape benchmark IPM-II are designed using the same stator, rotor diameters and PM usage by global parametric optimization. Their electromagnetic performance is compared. It confirms that the proposed AIPM has the highest maximum torque. It is also revealed that the torque enhancement is achieved by both 1.5-layer structure and MFS effect.