Nowadays, hybrid electric vehicles (HEVs) have been employed and developed extensively for promoting the rapid development of resource-conserving and environment-friendly society. Due to the multi-mode operations of the HEVs, the high integrated electric drive system with the motors which features the high torque density, high efficiency, and wide speed range are becoming the main trend in the HEVs. In this paper, a partitioned-rotor and staggered-stator hybrid excited flux switching permanent magnet（PS-HEFSPM）motor is proposed for hybrid vehicles, in which the air-gap field can be easily controlled.
The PS-HEFSPM motor consists of 12-stator and 10-rotor poles, in which the NdFeB permanent magnets and the DC field windings both serve as magnetic excitation sources. The partitioned rotor consists of two parts of inner and outer portion, which are connected together by an end disc to realize the same operating speed. The adoption of this unique partitioned rotor configuration effectively obtains the high torque density and avoids the stator flux leakage. Furthermore, the staggered stator of the proposed motor includes two salient pole parts staggered at a certain angle on the circumference, as well as the 12-rectangular magnetic bridges which connect the two salient pole parts in radial direction. The merits of this new stator structure are forming series magnetic circuit which runs through two rotors smoothly and creating space for the field windings which are wound around each rectangular magnetic bridge to fulfill the flux-adjusting function by controlling and changing the polarity and amplitude of the field current.
Firstly, the operation principle of the PS-HEFSPM motor is introduced and the initial design parameters are given. Then, in order to improve the flux regulation capability of the motor, the leading parameters are optimized by multi-objective optimization method. Moreover, the basic electromagnetic performances including back-EMF, torque, as well as torque–speed and power–speed characteristics are analyzed by 2D-FEA. Thereafter, it shows that after the targeted optimization design, the flux regulation capability reaches a high level, which meet the application requirements.