Magnetic Circuit Model and Performance Analysis of a V-Type Hybrid Permanent-Magnet Variable- Flux Machine

The permanent-magnet variable-flux machine (PM-VFM) is a promising candidate in the application of extended-speed operation. In this paper, a V-type hybrid PMVFM which utilizes AlNiCo magnet to enable the magnetization state regulation and the NdFeB magnet to enhance the power density is investigated. The magnetic circuit models (MCMs) of the machine under positive magnetization state and negative magnetization state are developed and solved iteratively. The calculated results of the air-gap flux density, open-circuit leakage flux factor, and the operating points of the AlNiCo magnet and the NdFeB magnet are obtained and compared with the simulated results of finite element analysis (FEA). The selection rules of dimensional parameters of hybrid PMs are investigated. To reduce the negative influence of the q-axis armature magnetic field on the electromagnetic performance of PM-VFMs, the effects of the q-axis flux barrier on the air-gap flux density, flux variation range (FVR) and torque characteristics are investigated. The mechanical strength of the rotor with q-axis flux barrier is verified.