Abstract
This article proposes a novel low-cost consequent-pole permanent magnet (CPM) synchronous machine structure, considering the reluctance torque utilization. First, a novel CPM machine with doubled salient ferromagnetic iron poles (ICP-PMSM) is proposed, featuring an N pole - iron - S pole - iron sequence to maximize the reluctance torque utilization and reduce cost. Flux barriers are integrated into the rotor structure to maintain the same magnetic rotor pole number as the conventional CPM synchronous machine (CP-PMSM). Second, for a low torque ripple, soft ferrite is used to replace part of the iron pole in the ICP-PMSM (ISCP-PMSM) to improve the air-gap flux density distribution. Furthermore, the CP-PMSM, ICP-SPMSM, and ISCP-PMSM rotors are optimized for a fair comparison. The electromagnetic performances of all the optimized machines are compared with those of a conventional surface permanent magnet synchronous machine (SPMSM). It is demonstrated that the ISCP-PMSM can obtain an almost equivalent torque and torque ripple, but with reduced PM (NdFeB) usage and cost when compared to the SPMSM.
Highlights
Permanent magnet (PM) machines have been widely developed for various industrial applications, including electric vehicles [1] and household appliances [2], owing to their high efficiency, high torque, and power density
In [13], a PM machine with a dovetailed consequent-pole rotor was proposed to reduce the volume of PM material and sleeve cost, while the average torque and efficiency can be improved owing to the reduced air-gap reluctance
2 Fm Rgm Rgip where Fm is the magneto-motive force (MMF) generated by the PM pole, Rm is the magnetic reluctance of the PM, and Rgm and Rgip are the magnetic reluctances of the air-gap facing the PM and iron pole, respectively
Summary
Permanent magnet (PM) machines have been widely developed for various industrial applications, including electric vehicles [1] and household appliances [2], owing to their high efficiency, high torque, and power density. Rotor asymmetry [12] was introduced to make full use of the reluctance torque at the zero-phase current angle and improve the machine performance. In [13], a PM machine with a dovetailed consequent-pole rotor was proposed to reduce the volume of PM material and sleeve cost, while the average torque and efficiency can be improved owing to the reduced air-gap reluctance. If it is applied to both the stator and rotor well, the torque density must be low Owing to this characteristic, using it in the motor core can help equalize the magnetic density distribution. The use of PM torque and reluctance torque in CPM machines is first proposed for maximizing the output torque at the zero-phase current angle; the torque performance can be further improved by using soft ferrite instead of part of the iron pole.
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