Experimental noise and vibration analysis of switched reluctance machines comparison of soft and hard chopping in transient conditions

This paper presents a comparison of soft and hard chopping on an 8/6 SRM in terms of noise, vibration and harshness. Transient-state measurements are used to plot speed-frequency signatures of current, vibration and acoustic noise of the SRM for different load torques. With this technique speed-related frequencies can be distinguished from resonance frequencies, and therefore, more information can be extracted from the plots. The results show that hard chopping increases the loudness of acoustic noise compared to soft chopping, with a frequency shift to higher values. This however leads to an attenuation of the vibration and noise amplitudes at the most critical resonance of the SRM, situated at a relatively low frequency.