US5514978A
Expired / Lapsed
US
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Stator turn fault detector for AC motor
Assignee: General Electric Co
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Filing: 1995-03-20
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Granted: 1996-05-07
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Expires: 2015-03-20
Abstract
Abstract Motor current and voltage waveforms are measured and converted to digitized current and voltage waveforms. A weighted discrete fourier transform is applied to the digitized current and voltage waveforms to obtain negative sequence current and voltage phasors; and the negative sequence current and voltage phasors are used to determine the existence of a turn fault. The use of the negative sequence current and voltage phasors can be performed by employing one of several techniques. In a first embodiment, an apparent negative sequence impedance is estimated by dividing the negative sequence voltage phasor by the negative sequence current phasor for comparison with a threshold negative sequence impedance. In a second, related embodiment, a current differential is estimated by dividing the negative sequence voltage phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence current phasor for comparison with a threshold current differential. In a third, related embodiment, a voltage differential is estimated by multiplying the negative sequence current phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence voltage phasor for comparison with a threshold voltage differential. In either of the second or third embodiments, the characteristic negative sequence impedance can be obtained by inserting a calibration device into one phase of the motor.
Inventors
- 👤 Rudolph A. A. Koegl
- 👤 William J. Premerlani
- 👤 Gerald B. Kliman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:49
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/34; G01R31/346; G01R19/00; G01R19/25; G01R23/00; G01R23/16; G01R27/00; G01R27/02; G01R27/16
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
86 words
A method for detecting turn faults in an induction motor comprising the steps of: obtaining motor current waveforms; obtaining motor voltage waveforms; converting the motor current waveforms to digitized current waveforms and the motor voltage waveforms to digitized voltage waveforms; applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain symmetrical component current phasors and symmetrical component voltage phasors; and determining the existence of a turn fault by employing the symmetrical component current phasors and symmetrical component voltage phasors.
Claim 2
Independent Claim
86 words
A method for detecting turn faults in an induction motor comprising the steps of: obtaining motor current waveforms; obtaining motor voltage waveforms; converting the motor current waveforms to digitized current waveforms and the motor voltage waveforms to digitized voltage waveforms; applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain symmetrical component current phasors and symmetrical component voltage phasors; and determining the existence of a turn fault by employing the symmetrical component current phasors and symmetrical component voltage phasors.
Claim 3
Dependent Claim
94 words
The method of claim 1, wherein the step of applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain symmetrical component current phasors and symmetrical component voltage phasors includes obtaining a negative sequence voltage phasor and a negative sequence current phasor; and wherein the step of determining the existence of a turn fault comprises estimating an apparent negative sequence impedance by dividing the negative sequence voltage phasor by the negative sequence current phasor, and comparing the estimated apparent negative sequence impedance with a threshold negative sequence impedance.
Claim 4
Dependent Claim
99 words
The method of claim 1, wherein the step of applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain symmetrical component current phasors and symmetrical component voltage phasors includes obtaining a negative sequence voltage phasor and a negative sequence current phasor; and wherein the step of determining the existence of a turn fault comprises estimating a current differential by dividing the negative sequence voltage phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence current phasor, and comparing the estimated current differential with a threshold current differential.
Claim 5
Dependent Claim
108 words
The method of claim 3, wherein the characteristic negative sequence impedance is obtained by a method comprising the steps of: inserting a calibration device into one phase of the motor; obtaining calibration motor current waveforms; obtaining calibration motor voltage waveforms; converting the calibration current waveforms to calibration digitized current waveforms and the calibration motor voltage waveforms to calibration digitized voltage waveforms; applying a weighted discrete fourier transform to the calibration digitized current waveforms and calibration digitized voltage waveforms to obtain a calibration negative sequence current phasor and a calibration negative sequence voltage phasor; and dividing the calibration negative sequence voltage phasor by the calibration negative sequence current phasor,
Claim 6
Dependent Claim
99 words
The method of claim 1, wherein the step of applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain symmetrical component current phasors and symmetrical component voltage phasors includes obtaining a negative sequence voltage phasor and a negative sequence current phasor; and wherein the step of determining the existence of a turn fault comprises estimating a voltage differential by multiplying the negative sequence current phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence voltage phasor, and comparing the estimated voltage differential with a threshold voltage differential.
Claim 7
Dependent Claim
108 words
The method of claim 5, wherein the characteristic negative sequence impedance is obtained by a method comprising the steps of: inserting a calibration device into one phase of the motor; obtaining calibration motor current waveforms; obtaining calibration motor voltage waveforms; converting the calibration current waveforms to calibration digitized current waveforms and the calibration motor voltage waveforms to calibration digitized voltage waveforms; applying a weighted discrete fourier transform to the calibration digitized current waveforms and calibration digitized voltage waveforms to obtain a calibration negative sequence current phasor and a calibration negative sequence voltage phasor; and dividing the calibration negative sequence voltage phasor by the calibration negative sequence current phasor.
Claim 8
Independent Claim
105 words
A method for obtaining a characteristic negative sequence impedance of an ac motor comprising the steps of: inserting a calibration device into one phase of the motor; obtaining calibration motor current waveforms; obtaining calibration motor voltage waveforms; converting the calibration current waveforms to calibration digitized current waveforms and the calibration motor voltage waveforms to calibration digitized voltage waveforms; applying a weighted discrete fourier transform to the calibration digitized current waveforms and calibration digitized voltage waveforms to obtain a calibration negative sequence current phasor and a calibration negative sequence voltage phasor; and dividing the calibration negative sequence voltage phasor by the calibration negative sequence current phasor.
Claim 9
Independent Claim
105 words
A method for obtaining a characteristic negative sequence impedance of an ac motor comprising the steps of: inserting a calibration device into one phase of the motor; obtaining calibration motor current waveforms; obtaining calibration motor voltage waveforms; converting the calibration current waveforms to calibration digitized current waveforms and the calibration motor voltage waveforms to calibration digitized voltage waveforms; applying a weighted discrete fourier transform to the calibration digitized current waveforms and calibration digitized voltage waveforms to obtain a calibration negative sequence current phasor and a calibration negative sequence voltage phasor; and dividing the calibration negative sequence voltage phasor by the calibration negative sequence current phasor.
Claim 10
Dependent Claim
21 words
The method of claim 7, wherein the calibration device comprises a device selected from the group consisting of resistors and inductors.
Claim 11
Independent Claim
113 words
An apparatus for detecting turn faults in an induction motor, the apparatus comprising: at least two current sensors for obtaining at least two motor current waveforms; at least two voltage sensors for obtaining at least two motor voltage waveforms; an analog to digital converter for converting the motor current waveforms to digitized current waveforms and the motor voltage waveforms to digitized voltage waveforms; a processor for applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain symmetrical component current phasors and symmetrical component voltage phasors, and for determining the existence of a turn fault by employing the symmetrical component current phasors and symmetrical component voltage phasors.
Claim 12
Independent Claim
113 words
An apparatus for detecting turn faults in an induction motor, the apparatus comprising: at least two current sensors for obtaining at least two motor current waveforms; at least two voltage sensors for obtaining at least two motor voltage waveforms; an analog to digital converter for converting the motor current waveforms to digitized current waveforms and the motor voltage waveforms to digitized voltage waveforms; a processor for applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain symmetrical component current phasors and symmetrical component voltage phasors, and for determining the existence of a turn fault by employing the symmetrical component current phasors and symmetrical component voltage phasors.
Claim 13
Dependent Claim
56 words
The apparatus of claim 9, wherein the processor includes means for obtaining a negative sequence voltage phasor and a negative sequence current phasor, estimating an apparent negative sequence impedance by dividing the negative sequence voltage phasor by the negative sequence current phasor, and comparing the estimated apparent negative sequence impedance with a threshold negative sequence impedance.
Claim 14
Dependent Claim
61 words
The apparatus of claim 9, wherein the processor includes means for obtaining a negative sequence voltage phasor and a negative sequence current phasor, estimating a current differential by dividing the negative sequence voltage phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence current phasor, and comparing the estimated current differential with a threshold current differential.
Claim 15
Dependent Claim
61 words
The apparatus of claim 9, wherein the processor includes means for obtaining a negative sequence voltage phasor and a negative sequence current phasor, estimating a voltage differential by multiplying the negative sequence current phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence voltage phasor, and comparing the estimated voltage differential with a threshold voltage differential.
Claim 16
Independent Claim
129 words
An apparatus for obtaining a characteristic negative sequence impedance of a motor, the apparatus comprising: at least two current sensors for obtaining at least two motor current waveforms; at least two voltage sensors for obtaining at least two motor voltage waveforms; a calibration device coupled between the motor and a respective one of the voltage sensors; an analog to digital converter for converting the motor current waveforms to digitized current waveforms and the motor voltage waveforms to digitized voltage waveforms; a processor for applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain a calibration negative sequence current phasor and a calibration negative sequence voltage phasor and for dividing the calibration negative sequence voltage phasor by the calibration negative sequence current phasor.
Claim 17
Independent Claim
129 words
An apparatus for obtaining a characteristic negative sequence impedance of a motor, the apparatus comprising: at least two current sensors for obtaining at least two motor current waveforms; at least two voltage sensors for obtaining at least two motor voltage waveforms; a calibration device coupled between the motor and a respective one of the voltage sensors; an analog to digital converter for converting the motor current waveforms to digitized current waveforms and the motor voltage waveforms to digitized voltage waveforms; a processor for applying a weighted discrete fourier transform to the digitized current waveforms and digitized voltage waveforms to obtain a calibration negative sequence current phasor and a calibration negative sequence voltage phasor and for dividing the calibration negative sequence voltage phasor by the calibration negative sequence current phasor.
Claim 18
Dependent Claim
21 words
The apparatus of claim 13, wherein the calibration device comprises a device selected from the group consisting of resistors and inductors.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-05-07 | 1999-11-06 | 2000-05-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-05-07 | 2003-11-06 | 2004-05-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-05-07 | 2007-11-06 | 2008-05-07 | $7700.00 | Window Closed / Lapsed |