Patent ID: 7081760

Claim:
A method of rotor fault diagnostics in an induction motor, where the motor includes a rotor and a stator, the rotor having a plurality of conductive bars and a stator having multiple phases drawing current from a power supply, the method comprising the steps of: detecting the terminal line voltage signals and phase current signals during operation of the motor; acquiring the voltage signals and the current signals at a predetermined sampling frequency; storing the sampled signals for a predetermined period; filtering the voltage and current signals by a predetermined cuttoff frequency; converting the phase current signal to apparent line current signals; converting the line voltage signals and the apparent line current signals into space vector form quantities; calculating a pendulous oscillation signal from the line voltage space vector angle and the apparent line current space vector angle; converting the pendulous oscillation signal from a time domain form to a frequency domain form; determining the fundamental component of the pendulous oscillation signal in the time domain, and its swing angle index, wherein the swing angle index is the peak to peak value of the fundamental component of the pendulous oscillation signal; and activating an alarm when the swing angle index exceeds a predetermined threshold value.