Fault Detection in Induction Motors Based on Current Signature Analysis

• US 20160266207A1
• Filed: 03/10/2015
• Published: 09/15/2016
• Est. Priority Date: 03/10/2015
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Inventors: Liu, Dehong
• Granted Patent: US 9,618,583 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G01R 31/346 Testing of armature or field windings
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: H02H 3/08 responsive to excess current responsive to abnormal temperature caused by excess current H02H5/04
• CPC Class Codes: H02H 3/46 responsive to frequency deviations
• CPC Class Codes: H02H 3/52 responsive to the appearance of harmonics
• CPC Class Codes: H02H 7/08 for dynamo-electric motors
• CPC Class Codes: H02H 7/0833 for electric motors with control arrangements
• CPC Class Codes: H02H 7/0854 responsive to rate of change of current, couple or speed, e.g. anti-kickback protection H02H7/0851 takes precedence

Abstract

A method detects faults during a steady state of an operation of an induction motor. The method measures, in a time domain, a signal of a current powering the induction motor with a fundamental frequency and determines, in a frequency domain, a set of frequencies with non-zero amplitudes, such that a reconstructed signal formed by the set of frequencies with non-zero amplitudes approximates the signal measured in the time domain. The determining includes a compressive sensing via searching within a subband including the fundamental frequency of the signal subject to condition of a sparsity of the signal in the frequency domain. The method detects a fault in the induction motor if the set of frequencies includes a fault frequency different from the fundamental frequency.

Claims

1. A method for detecting faults during a steady state of an operation of an induction motor, comprising:

measuring, in a time domain, a signal of a current powering the induction motor with a fundamental frequency;

determining, in a frequency domain, a set of frequencies with non-zero amplitudes, such that a reconstructed signal formed by the set of frequencies with non-zero amplitudes approximates the signal measured in the time domain, wherein the determining includes a compressive sensing via searching within a subband including the fundamental frequency of the signal subject to condition of a sparsity of the signal in the frequency domain; and

detecting a fault in the induction motor if the set of frequencies includes a fault frequency different from the fundamental frequency, wherein steps of the method are performed by a processor.

2. The method of claim 1, further comprising:

controlling a supply of the current to the induction motor based on an outcome of detecting the fault.

3. The method of claim 1, further comprising:

interrupting supplying the current in response to detecting the fault.

4. The method of claim 1, further comprising:

determining a type of the fault based on an amplitude of the pair, wherein the type includes one or combination of a partial broken bar and a number of broken bars.

5. The method of claim 4, wherein the type of the fault is the partial broken bar if the amplitude of the fault frequency is less than a threshold.

6. The method of claim 4, further comprising:

determining a set of thresholds, each threshold in the set corresponds to a value of the number of broken bars; and

comparing the amplitude of the pair with the set of thresholds to determine the number of the broken bars.

7. The method of claim 1, wherein the measuring includes sampling the signal with a sampling rate of at least twice of the fundamental frequency of the signal, wherein the sampling is performed on a uniform grid to produce a set of samples for a grid of frequencies, and wherein the compressive sensing includes a high resolution off-the-grid compressive sensing including a searching for a frequency between adjacent samples on the grid of frequencies.

8. The method of claim 1, wherein the compressive sensing comprises:

searching for the set of frequencies with non-zero amplitudes using a gradient search with atomic norm constraints representing the sparsity of the signal.

9. The method of claim 1, wherein the reconstructed signal is determined based on measuring the signal for a period of time less than one second.

10. A system for operating an induction motor having a stator and rotor bars, comprising:

a power supply for powering the stator of the induction motor with a stator current having a fundamental frequency;

a sensor for measuring, in a time domain, a signal of a stator current powering the induction motor, wherein the measuring includes sampling the signal for a period of time during a steady state of the operation of the induction motor with a sampling rate of at least twice of a fundamental frequency of the stator current;

a processor for determining, in a frequency domain, a set of frequencies with non-zero amplitudes, such that a reconstructed signal formed by the frequencies with corresponding amplitudes approximates the signal measured in the time domain, wherein the determining includes searching within a subband including the fundamental frequency subject to condition of a sparsity of the signal in the frequency domain, and;

a user interface for signaling the fault, if the set of frequencies includes a fault frequency approaching the dominant frequency.

11. The system of claim 10, wherein the processor compares comparing the amplitude of the fault frequency with a threshold to determine a type of the fault, and wherein the user interface renders the type.

12. The system of claim 10, wherein the reconstructed signal is determined based on measuring the signal for a period of time less than one second.

13. The system of claim 10, wherein the processor commands the power supply to interrupt supplying the current in response to detecting the fault.

14. The system of claim 10, wherein the sensor samples the signal on a uniform grid with a sampling rate of at least twice of the fundamental frequency of the signal to produce a set of samples for a grid of frequencies, and wherein the compressive sensing includes a high resolution off-the-grid compressive sensing including a searching for a frequency between adjacent samples on the grid of frequencies.

15. The system of claim 10, wherein the compressive sensing uses a gradient search with atomic norm constraints representing the sparsity of the signal.