Low-cost direct instantaneous torque control for switched reluctance motors with bus current detection under soft-chopping mode

This study proposed a low-cost torque distribution function (TSF)-based direct instantaneous torque control (DITC) technique for switched reluctance motors (SRMs) by bus current detection under soft-chopping mode. A three-phase 12/8-pole prototype SRM is employed to analyse the phase currents and operation states, and a new converter connection with bus current sensor placement strategy is presented to replace the phase current sensors in each phase leg. Considering that the conventional bus current contains both the chopping current and demagnetisation current, the current sensor is placed in a new bus to remove all the needless demagnetisation currents. To obtain the chopping current information from the bus current for DITC implementation, pulse-width modulation signals with extremely short turn-off time are injected into the lower transistors to insert the chopping current detection states for brief intervals during each fundamental frequency cycle. The DITC scheme is implemented directly on the detected chopping currents from bus current based on a sinusoidal TSF. The proposed DITC system is more compact and low cost by using just a bus current sensor. The effectiveness of the proposed technique is verified by the simulation and experimental results.