Analyses On Electromagnetic Performance And Vibration And Noise Of Permanent Magnet Synchronous Motors For Vehicles

The calculation of electromagnetic performance and vibration and noise caused by the radial electromagnetic force of the permanent magnet synchronous motor for vehicles involve several complex physical fields,and the physical fields are interconnected and interacted with each other to determine the performance of the permanent magnet synchronous motor.Aiming at this problem,a permanent magnet synchronous drive motor with rated power of 60 kW is taken as the research object.Based on the multi-physics coupling platform,the electromagnetic performance of the prototype is analyzed,and the electromagnetic vibration and noise of the prototype at a certain working point are predicted.The bench test of the prototype verified the calculation results.Firstly,based on the assumption of the electromagnetic field of permanent magnet synchronous motor,the coupling calculation method of multi-physics of permanent magnet synchronous motor is theoretically explained.The magnetic density distribution characteristics in air gap are analyzed from the magnetic motive force of the stator and rotor.The spatial distribution and frequency characteristics of the radial force wave acting on teeth surfaces of the stator are obtained.The method of solving the structural mode and modal types of the motor are introduced.The radial force wave is used as the excitation,the vibration response of the shell surface and the electromagnetic noise can be calculated with the modal of the motor.Then,the two-dimensional finite element electromagnetic model of the prototype is established,and the static and transient electromagnetic fields are calculated respectively.The influence of notch width on the radial electromagnetic force under no-load condition is studied,and the radial electromagnetic force with rated speed is analyzed under peak load conditions.The simulation results of electromagnetic field show that the electromagnetic performance of the prototype can meet the design requirements,and the simulation results are compared with the experimental results.The radial electromagnetic force characteristics with the different notch widths under no-load conditions are studied,the results show that the notch width has influences both on the space and time distribution of electromagnetic force.Under the peak load condition,the ideal three-phase sinusoidal current is used as input,the radial electromagnetic force at rated speed is calculated,and its spatial order and frequency characteristics are analyzed.Then,the three-dimensional geometric model of the prototype is established.Based on the orthogonal test method,the influence of the motor structure on the natural frequency of the eighth-order radial mode of the stator core and stator assembly is studied,and the constrained mode of the stator assembly is solved.The analysis of the 8th order radial mode natural frequency of the stator core shows that the yoke thickness of stator is extremely significant,while the axial length and the skew angle are not significant.The analysis of the 8th order radial mode natural frequency of the stator assembly show that the ribs on the front end cover,the water channel in the shell and the junction box on the rear end cover are not significant.The modal of the stator assembly under the constraint condition is solved,and radial modes which have an influence for the electromagnetic vibration and noise are extracted.Finally,the vibration response and the radiated noise of the shell surface are calculated by the multi-physics coupling platform,and the experimental noise spectrum map is compared and analyzed.The two-dimensional radial electromagnetic force is extended into the three-dimensional distribution along the axial direction of the motor and loaded onto the teeth surfaces of the stator.The vibration response of the stator assembly structure under the radial electromagnetic force with some specific frequencies is calculated by the modal superposition method.The result shows a significant peak at 6400 Hz.The acoustic pressure level distribution of electromagnetic noise is calculated by the acoustic boundary element method.The result shows the noise peaks at 6400 Hz,and the noise amplitude in the low frequency region is significantly larger than the high frequency region.The experimental spectrogram of the prototype also shows that the motor has a resonance band at the frequency of 6100Hz-6300 Hz,which is close to the simulation result.The experimental noise is 69dB(A)and the simulation noise is 65.4dB(A),so the error between the two is not large.