Motor stator condition analyzer
First Claim
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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 (X2) and the effective negative sequence resistance (R2) to predetermined values whereby a predetermined difference between either X2 and R2 and the respective predetermined value is indicative of a stator winding fault.
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Abstract
A motor performance analyzer senses currents and voltages applied to the motor, converts the sensed signals to digital data signals, and stores the digital data signals. The analyzer includes a processor for evaluating the digital data and a display for alerting a user or technician to potential winding faults. Advanced signal processing techniques are used to further evaluate stored data and to provide trending information.
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Citations
5 Claims
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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:
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(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 (X2) and the effective negative sequence resistance (R2) to predetermined values whereby a predetermined difference between either X2 and R2 and the respective predetermined value is indicative of a stator winding fault. - View Dependent Claims (2, 3, 4, 5)
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