Optimum Design And Demagnetization Analysis Of Permanent Magnet Synchronous Motor For Vertical Mill Drive

The traditional vertical mill drive system usually uses the three-phase asynchronous motor as the power source.This kind of motor has the disadvantage of being unable to output large torque at low speed,and needs to rely on the turning over system and reducer to complete the start,which leads to the increase of the overall cost of the motor and reduces the economy of production and operation.In this dissertation,permanent magnet synchronous motor(PMSM)is used instead of three-phase asynchronous motor to form a permanent magnet direct drive system,without the use of turning system and reducer,reduce the complexity of the starting system,more reliable operation,and has the advantages of high efficiency,energy saving and high power factor.Therefore,the design and research of permanent magnet synchronous motor for vertical mill driving is of great significance for practical engineering.In this dissertation,a permanent magnet synchronous motor with rated power of650 k W and rated speed of 200r/min is designed according to the performance requirements of permanent magnet synchronous motor for vertical mill drive.According to the working principle of PMSM and the working characteristics of the vertical mill drive motor with low speed and large torque,the primary electromagnetic design of PMSM is carried out.Through the establishment of two-dimensional finite element model of permanent magnet synchronous motor,the influence of different structural parameters on the motor performance was studied,providing a theoretical basis for the motor structure optimization.The PMSM for vertical mill driving was further optimized.With the efficiency,power factor,torque ripple and permanent magnet eddy current loss of the motor as optimization objectives,reasonable optimization variables were selected and corresponding constraint conditions were set.Finite element calculation was carried out for the experimental scheme designed by Box-Behnken Design combination,and the mathematical model between the optimization target and the optimization variables was established by the response surface method.The particle swarm optimization algorithm was used to optimize the fitted response surface model,and the optimized variable parameters were obtained.The finite element model was established according to the optimized parameters.Verify the rationality of algorithm optimization.Aiming at the optimized electromagnetic scheme a prototype is made,and the stator current,output power and other performance parameters are compared and analyzed by experiments.Irreversible demagnetization of permanent magnet is a key problem that permanent magnet synchronous motors need to pay attention to.During the operation of the motor,various abnormal working conditions may occur,resulting in the change of the working point of permanent magnets,and in serious cases,the output performance of the motor will be reduced.This dissertation based on the special point observation method and the magnetic density observation line method,the demagnetization analysis of permanent magnets under three working conditions of motor phase break,three-phase short circuit and sudden load change is carried out.The effects of load mutation,initial load torque and ambient temperature of permanent magnet on demagnetization of permanent magnet under different working conditions were analyzed,and the changes of motor speed,torque and stator winding current under different working conditions were calculated and analyzed.