Rotor position sensing in switched reluctance motor drives by measuring mutually induced voltages

This paper describes a new method of indirect rotor position sensing for switched reluctance motor (SRM) drives. The principle is based on measuring the mutually induced voltage in an inactive phase which is either adjacent or opposite to the energized phase of an SRM. The mutual voltage in the “off” phase, induced due to the current in the active phase, varies significantly as the rotor, corresponding to the energized stator, moves from its unaligned position towards complete alignment. This mutually induced voltage variation is captured by a simple electronic circuit and then processed in a microcontroller to determine the commutation instants, thereby eliminating the need for direct rotor position sensors in an SRM. Successful operation of a four-phase SRM drive has been demonstrated in the laboratory using the mutual voltage (MV) technique of indirect rotor position sensing. The theoretical aspects of mutually induced voltages in an SRM and the relevant experimental results are presented in this paper