A new method to detect the initial position for sensorless SRM

To know the rotor initial position is a key factor to start the SRM without inversion. There are some methods to detect the initial position of sensorless SRM. For example, phase current method, phase inductance method, test coil method and so on. In this paper we proposed a new way to detect the initial position, which is based on analysis of the mutual inductance. When we add excitation to one phase, and measure the mutually induced voltage in an inactive phase which is adjacent to the energized phase of SRM. The mutual voltage depends on the excitation current and rotor position. If the current is a constant , the voltage will change with the rotation of the rotor which causes the coupling area between the active phase and the inactive phase. We could determine the rotor initial position by comparing the voltages generated by the two adjacent phases. The feasibility and reliability of the method is proved by the experiment of four-phase 8/6 pole SRM.