Induction machine broken-bar fault diagnosis using the rotor magnetic field space vector orientation

A new technique based on rotor magnetic field space vector orientation is presented to diagnose broken-bar faults in induction machines operating at steady state. In this technique, stator currents and voltages are used as inputs to compute and subsequently observe the rotor magnetic field orientation, which has a more significant "swing-like" pendulous oscillation in case of broken-bar faults than in healthy operation. It is shown here that the range of this "pendulous oscillation" is a function of the number of broken-bars. Also in this technique, it was found that an inter-turn shorted stator-winding fault, which exhibits similar pendulous oscillation, could be distinguished from rotor broken-bar faults through the use of a variance index. In order to validate this method, experimental evidence is given here for several broken-bar cases in a 2-hp, 3-phase, 2-pole, squirrel cage induction machine.