US 12,480,994 B2Granted

System and method for detecting broken-bar fault in squirrel-cage induction motors

AssigneeMitsubishi Electric Research Laboratories, Inc.

InventorDehong Liu

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Abstract

A computer-implemented method is provided for detecting broken bar faults of an induction motor during operations. The method includes steps of injecting a frequency modulation continuous wave (FMCW) voltage signal to the voltage source to power the motor, acquiring, in a time domain, a signal of a stator current powering the induction motor via an interface, performing Fourier Transform (FT) on the stator current and the injected FMCW signal to get spectra of the stator current and the injected signal, computing cross correlation between the spectrum of injected signal and the spectrum of stator current, extracting a fault signature at frequency f=±2(1−s)f0 in the cross-correlation function, and detecting a broken-bar fault in the induction motor if the fault signature magnitude is greater than a threshold.

Claims20

Dependent claims

A computer-implemented fault signal measuring method for detecting broken bar faults during operations of an induction motor powered by a stator voltage, wherein the method uses a processor coupled with a memory storing instructions implementing the method, wherein the instructions, when executed by the processor, carry out at steps of the method, comprising:

injecting frequency modulated continuous wave (FMCW) signals to the induction motor being operated via an interface, wherein the FMCW signals are modulated such that the FMCW signals are superimposed on a fundamental frequency of the stator voltage;
acquiring, via the interface, a response current signal for a frequency sweep period, wherein the induction motor generates the response current signal in response to the injected FMCW signals;
performing spectrum analysis of the injected FMCW signals and the response current signal of the induction motor;
computing cross correlation between a stator current frequency spectrum of the induction motor and a frequency spectrum of the injected FMCW signals;
extracting fault signature of broken bar fault from a result of the computed cross-correlation;
and
determining that a broken bar fault takes place in the induction motor if a magnitude of the fault signature is greater than a threshold.

4 more elements

A fault-detection apparatus for detecting broken bar faults during operations of an induction motor powered by a stator voltage, comprising:

an interface connected to a frequency modulated continuous wave (FMCW) generator and configured to cause a controller of the induction motor to add FMCW signals to the stator voltage via the FMCW generator;
a memory configured to store instructions of a computer-implemented fault signal measuring method for detecting broken bar faults during operations of an induction motor powered by a stator voltage;
and
a processor coupled with the memory, wherein the processor is configured to execute the instructions implementing the method, wherein the method comprises:
injecting, via the interface, the FMCW signals to the stator voltage of the induction motor, wherein the FMCW signals are modulated such that the FMCW signals are superimposed on a fundamental frequency of the stator voltage;
acquiring, via the interface, a response current signal for a frequency sweep period, wherein the induction motor generates the response current signal in response to the injected FMCW signals;
performing spectrum analysis of the injected FMCW signals and the response current signal of the induction motor;
computing cross correlation between a stator current spectrum of the induction motor and a current spectrum of the injected FMCW signals;
extracting fault signature of broken bar fault from a result of the computed cross-correlation;
and
determining that a broken bar fault takes place in the induction motor if a magnitude of the fault signature is greater than a threshold.

8 more elements

Dependencies are inferred from the claim text.