Research On Torque Characteristics Of Doubly Salient Electro-magnetic Brushless DC Motor

The doubly salient electro-magnetic(DSEM)brushless DC machine possesses advantages such as structure simplicity,high reliability,low cost,field regulation flexibiliy,and rotor robustness.Hence,it has profound application in industry,especially under harsh and high-speed environment.However,on account of nonlinear characteristics,control complexity and demands for real-time controlling,the existing control methods are not good enough as the power and efficiency still can be improved.Therefore,the torque characteristics of the DSEM motor are studied in this paper.The production mechanism and characteristics for torque and torque ripple of the DSEM motor are investigated,which provided references for proposing optimized methods on motor structure or control strategies.Firstly,structure and mathematical model of the DSEM motor are introduced,as well as the operation principles and several angle control strategies.The compositions of output torque are analyzed.Comparisons are made between DSEM motor and SRM(Switched Reluctance Machines)on torque-angle characteristics,current density and copper loss.The mechanisms of torque ripple are investigated from static and dynamic prospective,which provides basis for future researches on torque characteristics.Secondly,the DSEM motor drive model is established by co-simulation of Ansoft Maxwell and Simplorer with the field-circuit coupling method,and current closed loop control based on Pulse Width Modulation(PWM)is realized by programming with Simplorer C Model.The influence of stator pole shoes on torque characteristics is studied.Thirdly,a new control strategy,namely phase-current compensation control(PCC)strategy,is analyzed in details to reduce torque ripple during commutation.It is verified that this method can suppress torque ripple and improve output torque.Meanwhile,the influences of different compensation angle,compensation ratio and excitation current on torque characteristics are also studied.The PCC method for the DSEM motor with widened rotor pole is also analyzed.Those results provide references for self-optimizing control with different parameters.Last but not least,experiments on PCC method are conducted based on the DSEM motor drive test platform.The validity of PCC method on suppression torque ripple is verified by comparing phase current waveforms in simulation and experiments.The influences of different control strategies,compensation angles,compensation ratio and excitation current on output characteristics are also verified through experiments.It is verified that adopting PCC method can significantly improve output torque,power and efficiency for the DSEM motor.