High-speed control of variable reluctance motors with reduced torque ripple

In electronically commutated variable reluctance (VR) motors the the windings of different phases are constantly switched on and off; the turn-on and turn-off delays of the winding currents significantly affect the motor torque ripple in high-speed applications. A mathematical model is presented to describe how the delays influence the output torque of the VR motor. To demonstrate the validity of the model, a three-phase linear VR motor with a fixed-advance commutator was controlled at high speed. Significant reduction of the torque ripple was observed by reducing the motor winding currents while the motor was speeding up. This torque model, together with a simple fixed-advance commutator, makes control of the VR motor with an inexpensive digital processor possible