Patent ID: 6308140
Filing Date: 2001-10-23
Classification: G01R

Abstract:
A method of identifying broken rotor bars in a polyphase induction motor, the motor including a number of pole pairs, by using an electrical signature of the motor, comprising the steps of:(a) simultaneously sensing an instantaneous current signal supplied to the motor as a function of time over a period of time for at least one electrical phase of the motor;(b) performing a Fourier Transform on the sensed current signal over at least a portion of the period of time to provide a current signal spectra;(c) locating a peak in the current signal spectrum at a fifth harmonic of line frequency;(d) locating a peak in the current signal spectrum at a fifth harmonic sideband of f.sub.line (5-2.multidot.s);(e) locating a peak in the current signal spectrum at a fifth harmonic sideband of f.sub.line (5-4.multidot.s);(f) locating a peak of the current signal spectrum at a fifth harmonic sideband of f.sub.line (5-6.multidot.s);(g) identifying the sideband peaks having an amplitude within a predetermined value of an amplitude of the located fifth harmonic peak, said identified sideband peaks indicating a broken rotor bar.