Patent ID: 8836256

Claim:
A drive system, comprising: a DC bus, a switched reluctance motor (SR motor), a power inverter coupled electrically between the DC bus and the SR motor, the SR motor comprising phases each of which is operable in operational modes, a voltage sensor coupled electrically to the DC bus to sense a DC bus voltage of the DC bus and output a DC bus voltage signal indicative thereof, current sensors, each current sensor coupled electrically to a respective phase of the phases of the SR motor to sense a phase current of that phase and output a phase current signal indicative of that phase current, and a control system coupled electrically to the voltage sensor and the current sensors, the control system configured to control the power inverter so as to activate the phases sequentially in electrical cycles and so as to operate each phase selectively in the operational modes, the control system configured to: receive the DC bus voltage signal and the phase current signals, determine for each of the phases which one of the operational modes is active, with respect to each of the phases, determine a phase voltage of that phase according to a function that is dependent on which one of the operational modes is active for that phase so as to differ between the operational modes and that is dependent on the DC bus voltage and the phase current for that phase, and determine an estimated total torque of the SR motor with respect to an electrical cycle of the electrical cycles as a function of an estimated total energy outputted to a rotor of the SR motor by the phases during the electrical cycle by calculating a phase power for each phase as a product of the phase current for that phase and the phase voltage for that phase, integrating the phase powers with respect to time for the electrical cycle, and dividing by an electrical angle of the electrical cycle.