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Motor condition and performance analyzer

  • US 6,308,140 B1
  • Filed: 06/06/2000
  • Issued: 10/23/2001
  • Est. Priority Date: 05/20/1996
  • Status: Expired due to Fees
First Claim
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1. 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 fline (5-2·

    s);

    (e) locating a peak in the current signal spectrum at a fifth harmonic sideband of fline (5-4·

    s);

    (f) locating a peak of the current signal spectrum at a fifth harmonic sideband of fline (5-6·

    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.

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