Design And Performance Analysis Of Stator Permanent Magnet Brushless Motor For Vacuum Dry Pump Drive

With the improvement of the level of science and technology in China,many industries need clean vacuum environment as the basis of their production,and the demand for vacuum dry pumps is increasing.Vacuum dry pump drive motor generally adopts asynchronous motor and permanent magnet synchronous motor,stator permanent magnet brushless motor as its drive motor almost no application.Vacuum dry pump drive motor works,the air gap vacuum degree is close to absolute vacuum,the rotor heat is difficult to dissipate,and the heat is conducted through the shaft to the bearing,which may cause the bearing to lock.Comparing with permanent magnet synchronous motors and asynchronous motors,there is no permanent magnet eddy current loss and squirrel cage winding loss on the rotor of stator permanent magnet brushless motor,which is helpful for reducing the temperature rise of the rotor and the bearing.To solve the problem of high temperature rise of the rotor and bearing of traditional vacuum dry pump motor,the stator permanent magnet brushless motor for vacuum dry pump driving is designed and analyzed in this thesis.Firstly,this thesis introduces the types of stator permanent magnet brushless motors,and chooses double salient permanent magnet motor(DSPM)as the motor studied.According to the technical requirements of vacuum dry pump driving motor,the structure design and material selection of the double salient permanent magnet motor are performed,and the effects of stator and rotor tooth width,air gap thickness and permanent magnet width on the torque ripple of the motor are analyzed.To compare the performance of motors,this thesis designs the permanent magnet synchronous motor and the asynchronous motor under the same conditions as the double salient permanent magnet motor in the shape size,power level,voltage level and rated speed.Secondly,a two-dimensional finite element simulation model is established according to the designed motor parameters,and the internal magnetic field distribution of the doubly salient permanent magnet motor under different conditions and the performance curve of the doubly salient permanent magnet motor under no-load and load are analyzed,it is compared with permanent magnet synchronous motor and asynchronous motor under rated operating conditions.The iron loss of stator rotor,copper loss of stator,eddy current loss of permanent magnet and aluminum loss of rotor with three kinds of motors are calculated respectively,and the losses of each part of three kinds of motors are compared and analyzed.Then,drawing software is used to draw the same housing and cooling waterways for the three motors.Based on the basic theory of heat transfer,the temperature field simulation analysis of the three motors in the rated working state is conducted under the same cooling system conditions,and it is concluded that the temperature distribution cloud diagram of the whole motor and each part is presented.The simulation results show that the temperature distribution of each part of the motor is reasonable.The temperature rise of the rotor and bearing of the double salient permanent magnet motor is lower than that of the permanent magnet synchronous motor and the asynchronous motor through the comparative analysis of the temperature of the three motors.Under the same technical requirements,a smaller doubly salient permanent magnet motor is designed,and its electromagnetic performance and temperature field are analyzed.Comparing the cost of materials consumed by different motor solutions,a more cost-effective motor solution is obtained.Finally,the thermal stress field of three kinds of motor bearings is simulated.Through the comparative analysis of the simulation results,it can be concluded that the thermal stress and thermal deformation of the bearing of double-convex permanent magnet motor are lower than those of permanent magnet synchronous motor and asynchronous motor,which can reduce the risk of bearing locking when the motor runs stably,and can effectively improve the stability and reliability of the operation of vacuum dry pump unit.