Sensorless Operation of SRM Drives
This chapter considers the study of a low-cost, sensor- or sensorless-based, current-and speed-controlled SRM drive system. The control of SRM drives depends on the phase current, absolute rotor position, and rotor speed signals to obtain closed-loop control of current (torque) and speed. The requirement of low cost with high performance for motor drives has placed the agenda of low-cost, sensor-based or sensorless technology at the forefront of present-day research and development of motor drives. SRM drives are no exception to this trend, as seen from the high degree of interest shown by industrial and academic researchers worldwide on this topic. Current control could be inexpensively achieved both with sensors and without sensors. The sensorless methods of estimation can be classified into modern control-based and inductance-based estimation schemes. The sensorless estimation scheme uses current rise and fall times to estimate the incremental inductance of the machine phase from which the rotor position is extracted.