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. An analog electronic technique can be used to measure the inductance of a nonconducting 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.<>