Research On Permanent Magnet Synchronous Motor For Traction Of Hevs

Thanks to the characteristics of high efficiency and power density, permanent magnet synchronous motor has become the most dominant type used as a HEV traction motor and has a wide application prospect.At the same time, in order to achieve the propulsion performance and energy use requirements, the motor should have excellent power and efficiency characteristics. Therefore there are still many areas for improvements in aspects of motor design, parameters calculation and research of related key technologies such as multi-points efficiency optimization in the whole work area, improvement of flux-weakening and peak power abilities. These are very different from traditional motor design and performance optimization. Currently, these issues have not been resolved comprehensively and reasonably so that the development of PMSM in HEVs is restricted.This paper will focus on parameters calculation and design method for performance improvements of PMSM in HEVs.For the PMSM models of different magnetic circuit structure, the torque-power angle characteristic is calculated and a analysis method of reluctance torque and reactance is proposed. Based on this a rational magnet circuit structure is selected for the prototype.Combined with related control strategy, the mathematical expressions of power characteristics in constant power area are derived. The effects on q-axis synchronous reactance of the ratio of tooth and slot width are analyzed. A specific measure is put forward to improve the flux-weakening ability based on optimization of saturation level of q-axis magnetic circuit.A design method of rotor eccentric circle based on analytical method and FEM is proposed. The effects on sine level of air-gap flux density of eccentric length, radius of eccentric circle and pole-arc coefficient are respectively analyzed so that the variation law of various of harmonic content is obtained.The restrictions to peak power ability of winding temperature rise and permanent magnet stability are analyzed. According to the results some measures of improving peak power ability of PMSM are proposed.A selection method of no-load back EMF in motor design process is put forward by analyzing the v-shaped curve from the point of efficiency optimization. The loss equations suitable for efficiency analysis at different operating points and the measure principle of location and extent of high efficiency zone are proposed. The effects on high efficiency area of movement of base-speed point are analyzed based on the principle.According to the above design method, a prototype is designed and manufactured combined with the theoretical analysis of related key technologies. A test bed is set up and the reactance, efficiency map, temperature rise and torque fluctuation of prototype are tested. The analysis is verified by the comparison of analysis, simulation and test results.