Rotor position detection with employment of the pulse injection technique on switch capacitors in switched reluctance motors

Abstract

This paper presents a new and novel method designed to detect rotor position by decoding received information in two different techniques for switched reluctance motor at standstill and also low speeds. These decoding techniques are namely, digital pulse width modulation (DPWM) decoder and digital pulse position modulation (DPPM) decoder. This method begins by connecting a small capacitor in series with each motor phase winding. The supply voltage in conjunction with the drive transistor produces a short pulse for each phase capacitor. Since the phase inductance varies with the rotor position, the rise time of the voltage produced on each capacitor changes as well. Next, the capacitor voltages are compared with some pre-set voltage values and the rotor position is detected at standstill mode. The number of pre-set voltage values varies for each technique. It then continues to sense the rotor position while the motor is running by applying the same procedure, but only to the un-energized phases windings. The results obtained demonstrate the feasibility and practicability of the method