Fault detection and diagnosis in an induction motor

Patent metadata

Field	Value
Publication number	US-2016266208-A1
Application number	US-201615050718-A
Country	US
Kind code	A1
Filing date	Feb 23, 2016
Priority date	Mar 9, 2015
Publication date	Sep 15, 2016
Grant date	—

Abstract

A method of detecting rotor and/or stator side faults in an induction motor. Signals indicative of three-phase stator currents of the induction motor are acquired ( 10 ) and converted ( 16 ) into three-phase current phasors. The three-phase current phasors are combined ( 16 ) to obtain a quantity having a DC component and an AC component. A frequency spectrum of the AC component is obtained ( 18 ) and compared ( 20,22 ) to a frequency spectrum of the AC component under healthy operating conditions in order to determine the presence of a rotor and/or stator side fault in the induction motor

First claim

What is claimed is:

1 . A method of detecting rotor and/or stator side faults in an induction motor, the method comprising:
i acquiring signals indicative of three-phase stator currents of the induction motor; ii. converting the signals indicative of three-phase stator currents into three-phase current phasors; iii. combining the three-phase current phasors to obtain a quantity having a DC component and an AC component; iv. obtaining a frequency spectrum of the AC component; and v. comparing the obtained frequency spectrum of the AC component to a frequency spectrum of the AC component under healthy operating conditions in order to determine the presence of a rotor and/or stator side fault in the induction motor.

2 . The method as claimed in claim 1 wherein the three-phase current phasors are combined by calculating the square root of the squared sum of the three-phase current phasors.

3 . The method as claimed in claim 1 , wherein a stator fault is detected based on a ratio of a fundamental supply frequency of the AC component to a harmonic of the fundamental supply frequency of the AC component.

4 . The method as claimed in claim 1 , wherein a rotor fault is detected based on sideband components of at least one harmonic of the fundamental supply frequency of the AC component that are present in the obtained frequency spectrum.

5 . The method as claimed in claim 1 comprising determining whether the acquired signals indicative of three-phase stator currents of the induction motor are steady state signals, prior to combining the three-phase current phasors.

6 . The method as claimed in claim 1 , comprising diagnosing the type of rotor and/or stator side fault.

7 . The method as claimed in claim 6 , wherein diagnosis of the type of stator fault is based on the magnitude of a fundamental supply frequency of the induction motor, and the magnitude of at least one harmonic of the fundamental supply frequency of the induction motor, for each phase.

8 . The method as claimed in claim 6 , wherein diagnosis of the type of stator fault is based on a ratio of the magnitude of a fundamental supply frequency of the induction motor to the square root of the sum of the magnitudes of harmonics of the fundamental supply frequency of the induction motor, for each phase.

9 . The method as claimed in claim 8 , wherein diagnosis of the type of stator fault is based upon the variance of the ratios of the magnitude of the fundamental supply frequency of the induction motor to the square root of the sum of the magnitudes of harmonics of the fundamental supply frequency of the induction motor of each phase.

10 . The method as claimed in claim 9 , wherein the stator fault is diagnosed as a voltage unbalance fault when the variance is less than 150% of the minimum ITHD value of all phases of a healthy induction motor and/or the stator fault is diagnosed as a stator winding fault when the variance is greater than 150% of the minimum ITHD value of all phases of a healthy induction motor

11 . The method as claimed in claim 6 , wherein diagnosis of the type of rotor fault is based on sideband components of harmonics of the fundamental supply frequency of the AC component.

12 . The method as claimed in claim 11 , wherein the rotor fault is diagnosed as a broken rotor bar fault when the power distribution of sidebands around a selected harmonic is below a specified threshold value and/or the rotor fault is diagnosed as an airgap eccentricity fault when the power distribution of sidebands around a selected harmonic is above a specified threshold value.

13 . The method as claimed in claim 1 , the method comprising:
i. converting each of the acquired signals indicative of three-phase stator currents of the induction motor into three-phase stator current frequency spectra; and ii. comparing the obtained three-phase stator current frequency spectra and/or the frequency spectrum of the AC component to spectra of the induction motor under healthy operating conditions in order to diagnose the type of rotor and/or stator side fault.

14 . A fault detector for an induction motor having one or more sensors thereon capable of acquiring signals indicative of three-phase stator currents of the induction motor, the detector comprising;
i. a receiver for receiving signals indicative of three-phase stator currents of the induction motor; ii. a signal convertor for converting the signals indicative of three-phase stator currents into three-phase current phasors and combining the three-phase current phasors to obtain a quantity having a DC component and an AC component to obtain a frequency spectrum of the AC component; and iii. one or more processor arranged to compare the obtained frequency spectrum of the AC component to a frequency spectrum of the AC component under healthy operating conditions in order to determine the presence of a rotor and/or stator side fault in the induction motor.

15 . A data carrier comprising machine readable instructions for the control of one or more processors of an induction motor fault detector to:
i. receive signals indicative of three-phase stator currents of the induction motor; ii. convert the signals indicative of three-phase stator currents into three-phase current phasors; iii combine the three-phase current phasors to obtain a quantity having a DC component and an AC component; iv. obtain a frequency spectrum of the AC component; and v. compare the obtained frequency spectrum of the AC component to a frequency spectrum of the AC component under healthy operating conditions in order to determine the presence of a rotor and/or stator side fault in the induction motor.

Assignees

• Rolls Royce Plc

Inventors

• Athikessavan Subash Chandar
• Nadarajan Sivakumar
• Gupta Amit Kumar
• Panda Sanjib Kumar
• Gajanayake Chandana Jayampathi

Classifications

• G01R31/346 Primary

  Testing of armature or field windings · CPC title

• H02P29/0241 Primary

  the fault being an overvoltage · CPC title