Magneto-thermal Coupling Analysis And Temperature Rise Study Of Permanent Magnet Synchronous Motors

Permanent magnet synchronous motors have the advantages of high efficiency,small size,and good control performance,so they have been used more and more widely.However,it is precisely the small size and high power density of PMSM that easily lead to the problem of excessive temperature rise of the motors.Excessive temperature rise of the motor will cause problems such as permanent magnet demagnetization and failure of the insulation material of the PMSM,which will greatly affect the service life and operating reliability of the motor.Therefore,it is particularly important to perform accurate simulation calculations and analysis of the temperature rise of PMSM.This article takes a 2.0k W industrial robot PMSM as the research object.According to the unidirectional coupling analysis method,the temperature rise calculation cannot reflect the mutual influence between the electromagnetic field and the temperature field of the motor,causing the shortcoming of calculation error.Corresponding analysis and research is carried out,and a bidirectional coupling analysis method is used to calculate the temperature rise of the motor.By comparing with the unidirectional coupling analysis results and prototype test results,it is proved that the bidirectional coupling analysis method can effectively improve the accuracy of the motor temperature rise calculation compared with the unidirectional coupling analysis method.The specific research work is as follows:Firstly,a finite element model of the electromagnetic field of the motor is established in the Maxwell,and then calculate and analyze the electromagnetic performance of the motor under no-load,rated load,and overload conditions,including back-EMF,air-gap magnetic density,magnetic density distribution,and so on,to verify the rationality of the motor design scheme for this subject.Secondly,the temperature characteristics of the motor permanent magnets and winding materials are analyzed.The loss of the motors at different temperatures is calculated and the law of the motor loss changes with temperature is studied under the conditions of temperature characteristics of the motor permanent magnets and winding materials.The results show that the temperature characteristics of the permanent magnet and the winding material will affect the motor loss when the motor temperature changes,and the motor loss is sensitive to the temperature.Based on this,the necessity of considering the influence of the temperature characteristics of the material of the motor on the calculation results in the calculation of the temperature rise of the motor is explained to improve the calculation accuracy.Furthermore,the unidirectional magneto-thermal coupling analysis method is used to calculate the temperature rise of the motor.Firstly,a three-dimensional simplified model of the motor temperature field was established,and the boundary conditions were established and the temperature field parameters were calculated according to heat transfer related theories and empirical formulas.Then,a unidirectional coupling model of the electromagnetic field and temperature field of the motor is constructed,and the temperature rise results of the motor are calculated and analyzed.The safety and reliability of the PMSM under rated operating conditions are verified by the calculation.Finally,the bidirectional magneto-thermal coupling analysis method is used to calculate the temperature rise of the motor.Firstly,a bidirectional coupling model of electromagnetic field and temperature field is constructed,and the interaction between the two fields is realized to reflect the mutual influence between the two fields,and the motor temperature rise is simulated and analyzed.Then,based on the test results of the prototype,the motor temperature rise simulation calculation results of two coupled analysis methods are compared and analyzed.The results show that compared with the unidirectional coupling analysis,the bidirectional coupling analysis effectively improves the accuracy of the motor temperature rise calculation,and its simulation results are closer to the test values.