A relationship of radial force sum and current waveforms in switched reluctance motor for noise reduction

In this paper, current command to reduce noise and vibration of switched reluctance motors have been investigated. Noise and vibration were reported to be significantly reduced by making a radial force sum as flat as possible with current profiling. In order to realize flat radial force sum, dc, fundamental, and second harmonic components were required. The dc and fundamental components are determined by torque requirement, thus, the second harmonic amplitude i₂ and phase shift φ₂ are adjusted to minimize variation of radial force sum of three-phase stator teeth. In this paper, i₂ and φ₂ are intentionally varied to see how radial force sum changes. Mathematical analysis is also carried. It was found that the third harmonic component is zero if i₂ and φ₂ are properly selected. The sixth harmonic component is also found to be limited. In addition 9, 12, 15, 18 and higher, and other harmonics 1, 2, 4, 5, 7, 8, 10, 11... are inherently zero, and only dc component remains. Effectiveness is verified in experiments in small size and full size test switched reluctance motors.