Claims
- 1. A method of evaluating stator condition of 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 for three electrical phases of the motor;
- (b) simultaneously sensing an instantaneous voltage supplied to the motor as a function of time for three electrical phases of the motor;
- (c) calculating an effective negative sequence reactance and resistance directly from the measured voltages and currents for each phase of the motor, without performing intermediate calculations of the negative sequence voltage or current;
- (d) comparing the effective negative sequence reactance (X.sub.2) and the effective negative sequence resistance (R.sub.2) to predetermined values whereby a predetermined difference between either X.sub.2 and R.sub.2 and the respective predetermined value is indicative of a stator winding fault.
- 2. The method of claim 1 wherein each predetermined value comprises a threshold designed to identify fast-degradation mechanisms based upon a large change in a fast period of time.
- 3. The method of claim 1 wherein each predetermined value comprises a threshold designed to identify slow-degradation mechanisms based upon a moderate change over a long period of time.
- 4. The method of claim 1 wherein the phase sequence of the motor is first examined to determine if the phase sequence is normal or reversed, and if reversed, exchanging phase B and C components, for both voltage and current prior to calculating the effective negative sequence reactance and resistance, in order to normalize the data.
- 5. The method of claim 1 wherein the predetermined valve are determined for each load category so that data is compared only for comparable loads.
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part of U.S. patent application Ser. No. 08/650,228, filed May 20, 1996 and entitled "Motor Condition And Performance Analyzer".
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
5270640 |
Kohler et al. |
Dec 1993 |
|
5514978 |
Koegl et al. |
May 1996 |
|
Non-Patent Literature Citations (2)
Entry |
"Conference Record of the 1989 IEEE Industry Applications Society Annual Meeting Part II", Papers Presented at the 1989 Industry Applications Conference Twenty-Fourth IAS Annual Meeting, Oct. 1-5, 1989. |
"Current Practices and Trends in Mechanical Failure Prevention", Proceedings of the 44th Meeting of the Mechanical Failures Prevention Group, Apr. 3-5, 1990, Complied by Henry C. Pusey and Sallie C. Pusey, a publication of the Vibration Institute. |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
650228 |
May 1996 |
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