Investigation of PWMs on vibration and noise in SRM with sinusoidal bipolar excitation

Vibration and acoustic noise are two critical issues for switched reluctance machine (SRM). The abrupt change of phase current mainly contributes to high vibration and noise under conventional unipolar excitation, sinusoidal bipolar excitation considered in this paper can suppress the vibration in SRM. However, to realize the smooth sinusoidal bipolar excitation, different pulse-width modulation (PWM) strategies can be employed. In this paper vibration and acoustic noise of a prototype 6/4 SRM under different load and speed, which employs hysteresis current control (HCC) and space vector pulse-width modulation (SVPWM), is investigated, together with the conventional unipolar excitation, which is modulated by voltage PWM. It shows that the lowest vibration and acoustic noise are obtained if the SRM excited by the sinusoidal bipolar excitation modulated by the SVPWM, regardless the speed and load. However, the HCC technique exhibits the worst vibration and acoustic noise due to random switching frequencies and mechanical resonances, although less sensitive to the load and speed. In contrast, the acoustic noise with the conventional unipolar excitation is sensitive to both load and rotor speed, when the sinusoidal bipolar excitation modulated by SVPWM is employed it is sensitive to the speed but not to the load.