Research On Three-Phase Asynchronous Motor Winding Change-over Speed Regulation System Based On DSP

In many AC motor drive applications such as EV and machine tool spindles,high torque at low speed as well as a broad speed range is required.However,maximum speed is restricted by rated voltage and power rating of the inverter,when using conventional flux-weakening methods.As for expanding motor speed range without raising inverter power rating,this paper firstly summarizes common winding change-over methods,taking three-phase asynchronous motor for example,stresses Yaskawa winding change-over method which expands speed range via lowering stator winding turns and EMF.Due to sudden changes of motor parameters when adopting this method,there's yet no effective way to analyze the transient or to cope with prospective consequences as current surge,torque disturbance and even breakdown of power devices.Thus,this paper adopts the tool of field-circuit coupling simulation,using Maxwell and Simplorer co-simulation to analyze the transient,to solve the problems of 9-lead motor modeling and control loop design.Simulation result accords with steady-state analysis,while the accuracy of its transient results remains to be tested by experiment.Besides,the motor torque can't exceed half the maximum output torque corresponding to the speed at the instant of winding change-over when using Yaskawa method,meanwhile,Yaskawa didn't elaborate how to make use of the EMF margin after winding change-over to further accelerate.To confront the issue above,an improved plan is proposed,i.e.,after constant ampere-turn change-over,raise the magnetizing current(for indirect vector control)or terminal voltage(for V/f control)to rated value,the transition for EMF and flux can be accomplished in very short time,after that,the motor can further accelerate by flux-weakening.To verify the co-simulation and the improved plan,a three-phase asynchronous winding change-over speed regulation platform based on DSP is built up,using V/f and indirect vector control as main control strategies.Then change-over experiment adopting constant ampere-turn control of magnetizing current is carried out.The result shows that transient current surge and torque disturbance are effectively ameliorated and the waveforms conform to those of the co-simulation.As for the improved plan,the transition time can be regulated by changing the rising speed of magnetizing current(terminal voltage)and can be lowered down to a matter of tens of milli-seconds.