ELIMINATION OF DISCRETE POSITION SENSOR AND CURRENT SENSOR IN SWITCHED RELUCTANCE MOTOR-DRIVES

Shaft position sensing is essential in switched reluctance motors (SRM) in order to synchronize the phase excitation pulses to the rotor position. In order to implement closed-loop torque control, current sensors are also unavoidable. These sensors can constitute a substantial portion of the total system cost and tend to reduce system reliability. A low-cost position-sensing scheme using stator inductance measurement is presented in this paper. An analog electronic technique can be applied to measure the inductance of a non-conducting phase by using a linear frequency modulated (FM) converter. The output of the FM converter is decoded to get the shaft position signal. The control functions and converter switching signals are processed in a low-cost microcontroller. The discrete current sensors for closed-loop operation have been eliminated by using MOS-gated power switches with integrated current sensing capability. The combination of the above two schemes resulted in a totally sensorless SR motor drive as described in the paper.