Demagnetization and Permanent-Magnet Minimization Anal-yses of Less-Rare-Earth Interior Permanent-Magnet Synchronous Machines Used for Electric Vehicles.

摘要

Rare-earth permanent magnet synchronous machines (RE-PMSMs) are widely used in electric vehicles (EVs) due to their characteristics of high efficiency, high torque density and high power factor. While the dramatic price fluctuations of the rare-earth permanent magnets (PMs) have been restricted the application of RE-PMSMs. Hence, the less-rare-earth interior permanent magnet synchronous machines (LRE-IPMSMs), which combine the features of high electromagnetic performance as well as low cost, have attracted increasing attention in recent years [1]. The anti-demagnetization ability of the LRE-IPMSMs is crucial to the machine safety [2]. In [3], the tapered flux barriers are adopted to improve the anti-demagnetization ability of the LRE-IPMSMs. In [4], a practical analytical approach is proposed to express the direct link between the PM thickness and the demagnetization limit. In addition, the PM minimization is also a significant issue for the LRE-IPMSMs as it is crucial to decrease the machine cost. In [5], an analytical procedure is proposed to reduce the PM quantity in the LRE-IPMSMs without affecting the torque versus speed performance. In this paper, the demagnetization equivalent magnetic circuit (EMC) model of the investigated LRE-IPMSM is established and the effects of structure parameters on the PM flux density are investigated. The PM minimization design of the LRE-IPMSMs is obtained on the premise of no side effect on the machine output toque and anti-demagnetization ability.