Sensorless Control for a Switched Reluctance Motor by Analysis of the Current Form

This paper presents a sensorless position control for switched reluctance motors (SRM). It is a waveform-based method where the inductance is determined from the current waveform. The main feature is the use of the current decay time during the freewheel phase using only the fundamental signals of the motor. The use of additional hardware, on the motor and in the inverter, is therefore not necessary. This allows sensorless control of the motor at low to medium speed. To start the motor, the pulse injection method known from the literature is used. A hysteresis controller adjusts the current in the individual phases depending on the speed and supplies the necessary time signals of the freewheel. These are used to evaluate the inductance of the winding and thus the position of the rotor. The theory is described, and the results of a prototype show the feasibility.