Demagnetization and permanent-magnet minimization analyses of less-rare-earth interior permanent-magnet synchronous machines used for electric vehicles

This paper investigates the demagnetization characteristic and permanent-magnet (PM) minimization of the less-rare-earth interior PM synchronous machines (LRE-IPMSMs) used for the electric vehicles, which are featured with high power density, high efficiency, and low cost. First, the equivalent magnet circuit (EMC) of the investigated LRE-IPMSM in demagnetization case is established. Then, the effects of the PM width and the thickness on the machine demagnetization characteristic are investigated. After that, the no-load EMC of the investigated LRE-IPMSM is established. Finally, an analytical method is proposed to obtain the minimum PM volume scheme on the premise of providing the targeted no-load flux and taking the machine anti-demagnetization ability into consideration simultaneously.