Dual-rotor Permanent Magnet Brushless DC Motor Finite Element Analysis And Fractional Slot Application

The subject of this study is part of the Natural Science Foundation of Shanxi Province,"The torque ripple reduction and the optimization of permanent magnet synchronous motor when the inverter supply power"(2013011035-1). The research topic of this paper is doing calculation and analysis of dual-rotar permanent magnet brushless DC motor (DR-PMBLDCM), which is used for boat driving.The dual-rotar permanent magnet brushless DC motor not only has inherited the advantages of traditional motor, it also has its unique advantages at the same time.It has broad application prospects in fields which has higher requirement for stability such as underwater propeller field. There exist some problems and drawbacks on the theoretical analysis and engineering design calculation.Because of the particularity of structure and operation mechanism of the dual-rotar permanent magnet brushless DC motor, the theoretical analysis about this motor is still lacking at present. The dual-rotar permanent magnent brushless DC motor which is bebing researched present has a defect that, its cogging torque amplitude is somehow bigger, it’s very necessary to improve the motor aim at reduce the cogging torque, from the structure design of motor.Therefore, in order to calculation and analysis the dual-rotar permanent magnent brushless DC motor more accurately and effectively, this paper completed following research contents:1. Established the model of dual-rotar permanent magnent brushless DC motor in the finite-element analysis software Ansoft Maxwell2D.The stastic and dynamic characteristics of the prototype was calculated, then the calculation results was analysised and the prototype was improved to reduce the dynamic torque ripple.2. This paper proposed a method named the radial air gap flux density function method, and established the model of prototype in Matlab/Simulink, which applied this method, by using the basic computing module and power module of Simulink, then compared the simulation results and the finite-element calculation results.The Simulink model of prototype provided the foundation for subsequent Performance and control strategy research of dual-rotar permanent magnent brushless DC motor.3. Applied fractional slot technology to dual-rotar permanent magnent brushless DC motor, in order to reduce the cogging torque ripple of prototype.Formulated several fractional slot projects which is suitable to prototype by taking restrictive conditions into account such as the unbalanced radial magnetic force, the possibilities of slots/poles combination and many other restrictive conditions.Finally respectively calculated these projects in Maxwell2D, and then the best fractional slot project for prototype was given. 4. Finished the analytic calculation for the prototype based on the combination of airgap permeability method and equivalent magnetic circuit method.Deduced the airgap permeability distribution function, which can satisfy the accuracy requirement, based on the Schwarz-Christoff transform method, and combined the airgap permeability distribution function and the equivalent magnetic path of each part of prototype.Compared the calculation result with finite-element calculation results, proved the correctness and feasibility of analytical calculation, and analyzed the reasons of differences between two results.5. Experimental platform of comprehensive performance testing has been designed. The relative speed balance, output torque of motor, efficiency of motor, stability of motor body temperature varies with the continuous running time of the prototype was respectively measured under different load levels. Simulinked the prototype model under corresponding modes in Matlab/Simulink, and compared the simulink results with experimental results, and analyzed the reasons of differences between two results.