Influence of switch angles on second-order current harmonic and resonance in switched reluctance motors

This study investigates the origin of resonance in switched reluctance motor (SRM). It has been found that the second-order harmonic component of phase current is one of the major origins, which may cause resonance when its frequency multiplied by three caused by three phases coincides with natural frequency. It has also been demonstrated that there is a natural-frequency-centred band, saying that as long as the excitation frequency or its harmonics locates in the band, resonance will be excited. Accordingly, influence of critical parameters such as turn-on and turn-off angles on second-order current harmonic and corresponding vibration caused by resonance have been fully studied. Based on the study, optimal switch angles can be used to reduce second-order current harmonic, and thus to reduce vibration and noise caused by resonance. Both simulation and experimental results show that resonance can be effectively reduced by selection of optimal switch angles.