Analysis and modeling of the radial force in a switched reluctance motor with sinusoidal excitations

Due to its special structure, the shaft radial force and torque of three-phase 12/8 switched reluctance motors can be independently controlled by proper distribution of currents at each pole of the excited phase. Radial force control is useful in balancing: 1) external force acting on the motor shaft, and 2) the imbalanced shaft force due to rotor eccentricity, so as to reduce motor vibrations. In this paper, the radial force and torque produced by the SRM under sinusoidal excitations are analyzed, and a scheme to produce the desired radial force is proposed. It was found that when excited with sinusoidal currents, the SRM can generate the desired shaft radial force in any direction in the rotational plane without interfering with the rotational torque. The scheme was verified with a finite-element analysis software and with an experimental system. Static experiments were performed, and the results have verified the effectiveness of the proposed scheme in controlling radial force of the SRM.