Novel rotor position estimation technique for switched reluctance motor (SRM)

Abstract

This article presents a new and novel method which is designed to detect the rotor position at standstill and at low speeds in switched reluctance motor. Since the inductance parameter plays a significant role both in the steady state and in the dynamic characteristics of an electromagnetic device, the rotor position can be determined using inductance bridge systems to measure unknown inductance and resistance values. In this method we use motor winding in Maxwell–Wien Bridge, with the standard capacitor and the resistor in parallel with it adjusted to achieve balance in an aligned position when the maximum inductance occurs. The supply voltage, in conjunction with the drive transistor, produces short pulses for this AC bridge. The condition of the balanced bridge v 0 = 0 leads to the relation between the impedances of the bridge branches. The phase inductance varies with the rotor position. Therefore the motor goes into an unaligned position and the Maxwell–Wien Bridge goes into an unbalanced condition thus causing variation in the state of the bridge output. It then continues to sense the rotor position with the motor running by applying the same procedure, but only to the un-energised phases winding. The simulation and experimentally obtained results demonstrate the feasibility and practicability of this method.