Design Optimization of Permanent Magnet DC Motors by Combining Calculation of Field and Circuit

　　Design Optimization of Permanent Magnet DC Motors by Combining Calculation of Field and Circuit
　　Due to the advantages of simple structure, small volume and high efficiency, permanent magnet direct current motors(PMDCMs) are applied widely in all fields of national economy. With the development of new structure, new material and new technology, the magnetic circuit structures of PMDCMs become more complicated and the traditional design method based on the magnetic circuit calculation can not ensure the design accuracy. So, the analysis and design optimization of PMDCMs are carried out with the idea of combining calculation of electromagnetic field and circuit in this thesis. The main work and achievements are as follows.Firstly, the electromagnetic field finite element models of PMDCMs are built up. Four main coefficients, including leakage flux coefficient at no load, airgap Neodymium Magnets coefficient, equivalent armature length and equivalent pole arc coefficient, are calculated respectively and the pole arc coefficient curves of PMDCMs with eccentric poles are given. Secondly, a new method to calculate the cogging torque is proposed. The validity of the method is verified by the test data. Thirdly, the effects of reducing cogging torque of PMDCMs with poles chamfering are researched by the new method. The results show that the cogging torque may reduced 79% at the optimal magnetic poles chamfering. Fourthly, the influences on armature reaction for PMDCMs with eccentric magnetic poles are calculated. The results show that the distortion factor of airgap magnetic field and the maximum voltage between the commutator bars can be reduced by eccentric magnetic pole. But eccentric http://www.999magnet.com/products/110-sintered-neodymium-magnets magnetic pole can not decrease the airgap flux density at commutation region. Finally, the design optimization model of PMDCMs is built up and an optimization software is developed by using particle swarm algorithm. The optimal results are obtained with the lower cost or higher efficiency.The research work is valuable at the aspects of improving the calculation accuracies of parameters and performances, investigating the effects of reducing the cogging torque and armature reaction with different permanent magnetic structures, as well as improving the performance and decreasing the cost of PMDCMs.