Rotor Position Detection in SRM Drive Utilizing Phase Shift Variations in a Formed Resonant Circuit

In switched reluctance motors, each individual phase excitation must be synchronized with the rotor position which necessitates the need for a position sensing scheme. This paper presents a complete and 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 technique in conjunction with the use of resonant scheme. A circuit consists of an external resistance R, motor phase inductance, L (thetas), and an external capacitance, C is formed and fed by a sinusoidal voltage having the same resonant frequency as the circuit. The current flowing through the resistor has the same frequency as the input voltage but can have different phase shift when compared to the input voltage due to die variation of phase inductance, L(thetas) which is directly proportional to rotor position. The produced resistor voltage waveform is then compared to the input sinusoidal voltage waveform in order to obtain 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. Finally, the paper presents the results obtained which demonstrates the feasibility and practicability of the method and outlines the advantages of this method.