Keywords: SR motors, torque ripples, gradient compensation, current modulation, power conversion, switched reluctance motors
Torque ripple minimisation in SR motors using phase inductance gradient compensation technique
The switched reluctance motor (SRM) is intended to operate in deep magnetic saturation to increase the output power density. Because of the saturation effect and the variation of magnetic reluctance with respect to rotor position, all the relevant characteristics of the machine are highly nonlinear functions of both rotor position and phase current. The ultimate outcome of all these nonlinearities is that the generated torque contains significant ripples. Determination of appropriate phase current profile for generating torque in SRM with minimum ripples poses a lot of difficulty owing to the nonlinear magnetic characteristics. A new method is introduced in this work that computes inductance gradient at each rotor position and phase current to modulate the phase current which produces zero torque ripples. The experimental results indicate that the torque ripple is reduced to lie within 5% of the desired steady torque even in dynamic operating conditions.