The Optimal Control Of Wound-rotor Permanent Magnet Synchronous Motor In Starting Process

At present, three-phase wound-rotor induction motor is widely used in the drive ofcranes. The starting performance of wound-rotor induction motor can be improved byadjusting the rotor external starting resistance. But, adjusting the resistance in steps willlead to the impact of the torque, and this can bring impact on mechanical system. Theefficiency and power factor of the wound-rotor induction motor will decrease with thereducing of load. Permanent magnet synchronous motor can maintain high power factorand efficiency in a wider range of load, but the cage self-starting permanent magnet motorcould not reach the requirements of overloading starting. In this paper, a Wound-rotorLine-start Permanent Magnet Synchronous Motor (WR LS-PMSM) was designed.WR LS-PMSM combines the advantages of wound-rotor induction motor and cageself-starting permanent magnet motor. This paper analyzes the designing features of theWR LS-PMSM, introduced the method of the optimal control of the WR LS-PMSM in thestarting process, and calculated the functional relation between series resistance and speed.Wrote the simulation calculation program of the motor in the starting process, the finiteelement method with field-circuit-movement coupling was used to simulate and calculateof the motor. Calculated the cure between average of the average torque and speed,analyzed the change of average torque in the starting process and the ability of pulling intosynchronous. The rotor winding of WR LS-PMSM can be connected with startingresistance through the slip ring and brush, the resistance in parallel with IGBT, IGBTchopper control was adopt to adjust the value of the resistance. In the process of starting,microcomputer detected the signal of rotor speed, and adjusted the IGBT on-off dutyaccording to the motor speed to change the value of the starting resistance smoothly, themotor can keep the maximum torque during the starting process. When the motor speedcloses to synchronous speed, the duty ratio of control signal of IGBT is1, the seriesresistance is completely removed. Experiment with WR LS-PMSM, including steady-statetest and dynamic performance test. In order to comparative analysis, do the same experiments on wound-rotor induction motor and cage self-starting permanent magnetmotor, analyzed the result of the experiment.The simulation results and the experimental results show that WR LS-PMSM cankeep the maximum torque during the starting process through the optimal control to thestarting resistance, and eliminated the impact torque. WR LS-PMSM starts more quicklyand smoothly and has the steady state characteristics of high efficiency and high powerfactor.