US 5,514,978 A · Stator turn fault detector for AC motor

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.

Claims14

Dependent claims

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.

3 more elements

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.

1 more element

Dependencies are inferred from the claim text.

Stator turn fault detector for AC motor

Life of this patent

Stator turn fault detector for AC motor

Life of this patent

Abstract

Claims14