A Control Strategy for SRM Drive to Produce Higher Torque and Reduce Switching Losses

Switched reluctance motors (SRMs) have been alternative solution for electric drives due to their simple construction, low cost in manufacturing and less maintenance although they have high ripple torque and require complicated control strategies. To generate higher torque of SRM for electric drive, the negative torque must be minimized by turning off the phase current as soon as possible after the aligned position between stator and rotor is achieved. A static converter is needed to give sequential excitation due to rotor position information. Some of converter topologies implement fewer switches to reduce losses produced by the switches. An asymmetric converter has some advantages because its phase leg can be independently controlled. The use a pair of switches in one leg will produce greater losses. A current control strategy is more appropriate for SRM drive due to the relationship between the torque and the phase currents of the motor. In this paper, a control strategy for asymmetric converter to drive an SRM is proposed. This control strategy is capable to operate the converter with lower switching losses and minimize the negative torque generated by the SRM. Simulation works were conducted to verify the analysis and finally the laboratory experiments were done to validate. They show the effectiveness of the proposed control strategy to drive the SRM.