Instantaneous shaft radial force control with sinusoidal excitations for switched reluctance motors

In general, unbalanced radial force acting on rotor shaft is undesirable since it causes vibrations. Due to its special structure, the shaft radial force and torque of a three-phase 12/8 switched reluctance motor can be separately controlled by proper selection of pole currents of the energized phase. In this paper, a sinusoidal current excitation scheme is proposed for the torque and radial force control of a 12/8 pole SRM. When controlled with the selected sinusoidal currents the SRM can produce the desired shaft radial force in any direction of the rotational plane without disrupting the rotational torque. Also, since the pole currents are individually controlled a more sophisticated phase commutation strategy is proposed for smoother torque and radial force ripples. The proposed schemes were verified experimentally.