E-motor NVH Analysis for PWM Induced Current Ripples in EV Applications

E-motors are one of the most important components in electric vehicles (EVs). They contribute as the main source of noise in EVs. For conventional e-motor NVH analysis, pure sinusoidal input currents are assumed. However, for motors under PWM control, significant noise can be observed at the switching frequency, which cannot be predicted using pure sinusoidal currents. In this paper, the NVH performance of e-motors is studied with a focus on the noise caused by the PWM-induced ripples in the current. It is found that the simulation time step plays an important role in predicting motor NVH. For low speeds finer time steps are needed while for higher speeds less time steps should be used for a quick simulation. A rule of thumb is proposed for 8-pole PMSMs on how to setup the suitable time steps based on the Nyquist sampling theorem. Finally, tests are conducted to validate the proposed theory.