Influence of PWM Current Harmonics on Electromagnetic Noise of External-Rotor In-Wheel Permanent Magnet Synchronous Motor for Electric Vehicle

PWM current harmonics causes high frequency noise of in-wheel permanent magnet synchronous motors (PMSMs) for Electric Vehicle (EV), which greatly impacts on comfort of the vehicle. In order to weaken the electromagnetic force harmonics caused by the PWM current harmonics and effectively suppress the electromagnetic noise of external-rotor in-wheel permanent magnet synchronous motor (PMSM) for electric vehicle, the speed-frequency characteristics law of the radial electromagnetic force were summarized. In order to improve the calculation accuracy of electromagnetic noise, a co-simulation model of “PWM Current-Electromagnetic Field-Structure Field” considering the influence of cross-coupling and magnetic saturation on inductance parameters was proposed. Taking a 36-slot 48-pole external-rotor in-wheel permanent magnet synchronous motor as a prototype, the electromagnetic noise with different switching frequencies (fc = 2kHz, 10kHz) were simulated and tested. The results show that the new noise harmonics generated by PWM current harmonics appear as scattering curve families, and each scattering curve family takes kfc (k=1,2,3,...) as its axis of symmetry in noise spectrum diagram. Properly increasing the switching frequency can reduce the noise and make the noise harmonic scattering curve families shift to the right and increase the interval in the spectrum diagram, which is an effective measure to suppress the electromagnetic noise generated by PWM current harmonics. The results of the prototype test verify the above conclusions. The theoretical basis and analysis method were provided for the prediction, evaluation and optimization of the noise of the external-rotor in-wheel PMSM powered by PWM current.