Modeling and control of a self-bearing switched reluctance motor

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. When all the pole currents are controlled independently, it is possible to control the radial force to counterbalance the external force acting on the shaft In this paper, a control scheme for self-bearing of a 12/8 pole SRM drive is proposed. The rotor needs only one bearing for rotation and to constrain the axial movement The other end can move freely in radial direction but is balanced with the radial force produced by the motor. Motor torque is controlled with the conventional method, but two additional poles in the phase with descending inductance are excited to produce the required radial force for rotor balancing. A model suitable for torque and radial force control is derived and then used for the synthesis of self-bearing control. The proposed control scheme is also implemented and verified experimentally.