Research On Optimal Design Of Wheel Permanent Magnet Motor With Rectangular Wave Forms

The finite element method is applied to analyze a prototype square wave permanent-magnet motors using in electric vehicles. The parameters, electromagnetic torques and characteristics of the machine are calculated, tested and analyzed systematically. A software package for optimum design of the motor based on an improved Tabu Search Algorithm and inverse problems of electromagnetic field is completed and used to reduce the price and weight of the motor.At first, the magnetic model of the prototype machine for numerical field calculation is formulated. The magnetic fields, the curves of counter EMF and coefficient of EMF for both straight and skewed slots are calculated. In the case of skewed slots, a subsection method is introduced especially. The self and mutual inductances are obtained by flux linkage method and energy method. The computed results are verified by the tested values.Then, the electromagnetic torques of the motor with y means of both methods, Maxwell's stress and virtual displacement methods, with straight and skewed slots are determined by Maxwell stress method and virtual displacement method. To reduce the computation error, the technics of mesh division are discussed. Moreover, the electromagnetic torques while the phase of current leads the EMF, and the oriented torques with straight and skewed slots are also calculated and discussed. Compared with test values, it is shown that the numerical results have satisfying accuracy.Based on the above investigation, the steady state circuit voltage equations established with the inductance voltage included. Compared with conventional formulation, the new one is accurate and useful for engineering practice.Finally, by using an improved Tabu Search Algorithm combined with inverse problems of electromagnetic field, the prototype machine is optimally designed and a software package is completed. The objective function and optimal variables are discussed. The numerical results show that the consumption of permanent-magnets for the optimized motor is reduced to a great extent compared with the original machine, thus leads to a significant reductions in motor price and weight. The software package is useful for sine wave PM synchronous motor also.