| Permanent magnet synchronous motors are widely applied in electric vehicles,industrial machine tools,military and other fields because of the high power density,large torque,high efficiency and other advantages.At present,most permanent magnet synchronous motors are driven by the inverter to achieve the speed control,but the big time harmonic component of the supply current leads to a big variety of the magnetic field harmonic wave,which generates a lot of eddy-current loss and harmonic iron loss and increases the heat source density of the motor.Meanwhile,excessive temperature rise may cause the demagnetization of permanent magnets due to the poor heat dissipation effect of the permanent magnets,which affects the motor performance directly and shortens the motor service life.Therefore,it is important to predict the temperature rise of the permanent magnet motors accurately in the motor design process.First of all,this paper proposes a method for calculating the bidirectional coupling between the electromagnetic field and the temperature field to achieve the iterative calculation of two fields of information and improve the motor temperature rise calculation accuracy considering the problem that the motor material property in the electromagnetic field changes with the variety of the motor temperature basing on the finite element method.A mathematical model of the bidirectional coupling of the electromagnetic field and the temperature field is established.The temperature rise of the motor prototype is calculated using the heat density loading method and the bidirectional coupling of the magnetic field and temperature field method respectively.The calculation results are compared and analyzed.The influence of the number of model division units on the accuracy of the calculation method is studied.Secondly,an interior permanent magnet synchronous motor is studied as an example.In order to ensure the adaptability of the motor in electromagnetic field and temperature field calculation,the motor model is simplified and the simulation analysis is implied on the prototype by the bidirectional coupling calculation method of electromagnetic field and temperature field.The temperature rise of the prototype is measured and the measured results are compared with the calculated results for verifying the accuracy of this method.In this paper,the permanent magnet axial average segmentation technique is adopted to theprototype,and the eddy current loss reduction of the permanent magnets and the suppression of the maximum temperature rise are calculated.The loss and the effect on temperature rise of different rotor structures are analyzed comparing the loss and temperature rise of the motors with V-and V-type rotor structures.Finally,the temperature rise of two surface-mounted permanent magnet synchronous motors is simulated using the bidirectional coupling method,and the calculated results are compared with the measured results.In this paper,the effect of stator core made of different materials on loss and temperature rise is studied,and the influence of the materials used for the motor casing and the insulation adhesive on the temperature rise of the motor is analyzed.The effect of the jacket made of different materials and copper shield ring on the loss and temperature rise of a high-speed permanent magnet synchronous motor is calculated and analyzed. |
