Design and optimization of a mechanical variable-leakage-flux interior permanent magnet machine with auxiliary rotatable magnetic poles

A novel mechanical variable-leakage-flux interior permanent magnet machine (MVLF-IPMM) is proposed for electric vehicles (EVs) in this paper, which employs a mechanical flux-regulating device and auxiliary rotatable magnetic poles. The magnetic poles acting as the flux adjustors can be rotated by the additional device to vary the leakage flux in magnetic circuit and realize the adjustment of the PM flux linkage. Due to the flux-regulating effect, the flux distribution in this machine is complex and changeable. Therefore, the working principle is illustrated in detail. To obtain the perfect coordination between the dominant magnetic poles and auxiliary magnetic poles, a multi-objective optimization method is presented based on the parameter sensitivity analysis combining with the Coefficient of Prognosis (CoP). Then, some design parameters with strong sensitive are selected by the sensitivity analysis and the initial model of the proposed motor is optimized by utilizing the multi-objective genetic algorithm (MOGA). According to the result of the optimization, the machine performances of the initial and the optimal design under the different flux states are compared and analyzed to verify the validity of the new variable-flux motor and the optimization method.