Rotor position detection in SRM drive by utilizing aligned rotor position resonant frequency

Abstract

This paper presents a novel method to indirectly detect the rotor position at standstill and also at low speeds in switched reluctance motor. The method utilizes current phase variation with respect to input voltage at a resonant frequency which is obtained at aligned rotor position. A circuit consists of an external sampling resistance R, motor phase inductance, L (0), and an external capacitance, C is formed and fed by a sinusoidal voltage having the aligned resonant frequency. Of course, there are two different selections for the resonant frequency namely, aligned or un-aligned rotor position inductances can be used. The current flowing through the resistor has the same frequency as the input voltage which is the resonant frequency but it can have different phase shift when compared to the input voltage due to the variation of phase inductance, L (0) which is directly proportional to rotor position. At resonant frequency the variations are large therefore; the produced resistor voltage waveform compared to the input sinusoidal voltage waveform can produce a pulse width proportional to the position of the rotor. The width of the pulse is determined accordance to the phase inductance which is directly proportional to the rotor position. In this paper aligned position inductance is employed for the detection of rotor position. Finally, the paper presents the results obtained which demonstrates the feasibility and practicability of the method and outlines the advantages of this technique.