Rotor fault and location detector for induction motors
First Claim
1. A method of detecting rotor faults in an induction motor, the motor including a stator and a rotor, the rotor including a multiplicity of rotor bars, the method comprising the steps of:
- generating a flux signal corresponding to the magnetic flux at a predefined flux detection point in the motor which is affected by the flux around each rotor bar in the motor as the rotor revolves;
generating a synchronization signal once each revolution of the rotor, said synchronization signal occurring when a predefined position on said rotor is closest to said flux detection point;
filtering said flux signal to reject signals in a predefined frequency band around and including the frequency at which the rotor bars pass said flux detection point; and
synchronously time averaging the output of said filtering step, using said synchronization signal as the synchronization reference for said averaging;
whereby statistically significant peaks in the output of said averaging step indicate the presence of a rotor bar fault, and the location of such peaks corresponds to the location of rotor bar faults with respect to said predefined position on said rotor.
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Abstract
A method and apparatus for detecting rotor faults in an induction motor. Such induction motors have a stator and a rotor comprising a multiplicity of rotor bars. The flux around the rotor bars is detecte at a predefined flux detection point in the motor, generally by using a coil wound around one of the stator teeth. A synchronization signal is generated once per revolution of the rotor when a predefined position on the rotor is closest to a stator reference point, usually the flux detection point. The detected flux signal is filtered to reject signals in a predefined frequency band around the frequency at which the rotor bars pass the flux detection point, and then it is synchronously time averaged. Averaging requires that corresponding portions of the flux signal, for a series of rotor revolutions, be added, and the synchronization signal is used as a reference for matching corresponding portions of the flux signal. Statistically significant peaks in the resulting time averaged signal indicate the presence of a rotor bar fault, and the location of such peaks corresponds to the location of rotor bar faults with respect to the predefined position on the rotor.
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Citations
23 Claims
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1. A method of detecting rotor faults in an induction motor, the motor including a stator and a rotor, the rotor including a multiplicity of rotor bars, the method comprising the steps of:
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generating a flux signal corresponding to the magnetic flux at a predefined flux detection point in the motor which is affected by the flux around each rotor bar in the motor as the rotor revolves; generating a synchronization signal once each revolution of the rotor, said synchronization signal occurring when a predefined position on said rotor is closest to said flux detection point; filtering said flux signal to reject signals in a predefined frequency band around and including the frequency at which the rotor bars pass said flux detection point; and synchronously time averaging the output of said filtering step, using said synchronization signal as the synchronization reference for said averaging; whereby statistically significant peaks in the output of said averaging step indicate the presence of a rotor bar fault, and the location of such peaks corresponds to the location of rotor bar faults with respect to said predefined position on said rotor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Apparatus for detecting rotor faults in an induction motor, the motor including a stator and a rotor, the rotor including a multiplicity of rotor bars, comprising:
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flux detection means, located at a predefined point on the stator in the motor, for generating a flux signal corresponding to the magnetic flux around each rotor bar in the motor as the rotor revolves; tachometer means for generating a synchronization signal once each revolution of the rotor, when a predefined position on said rotor is closest to said flux detection point; filter means for filtering said flux signal to reject signals in a predefined frequency band around and including the frequency at which the rotor bars pass said flux detection point; and computer means for synchronously time averaging the output of said filter means, using said synchronization signal as the synchronization reference for said averaging, and thereby generating an average flux signal; whereby statistically significant peaks in said average flux signal indicate the presence of a rotor bar fault, and the location of such peaks corresponds to the location of rotor bar faults with respect to said predefined position on said rotor. - View Dependent Claims (12, 13, 14, 15, 16)
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17. Apparatus for detecting rotor faults in an induction motor while the motor is in operation, the motor having a rotor with a multiplicity of rotor bars, comprising:
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flux detection means for generating a flux signal corresponding to the magnetic flux around the rotor bars in the motor as the rotor revolves; tachometer means for generating a synchronization signal once each revolution of the rotor, when the rotor is at a predefined position in the motor; filter means for filtering said flux signal to reject signals in a predefined frequency band around and including the frequency at which the rotor bars pass a fixed point in the motor, thereby generating a filtered flux signal; and averaging means for synchronously time averaging said filtered flux signal, using said synchronization signal as the synchronization reference for said averaging, thereby generating an average flux signal; whereby statistically significant peaks in said average flux signal indicate the presence of a rotor bar fault, and the location of such peaks corresponds to the location of rotor bar faults with respect to said predefined position on said rotor. - View Dependent Claims (18, 19, 20)
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21. A method of detecting rotor faults in an induction motor, the motor including a stator and a rotor, the rotor including a multiplicity of rotor bars, the method comprising the steps of:
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generating a flux signal while operating said motor to drive a load, said flux signal corresponding to the magnetic flux at a predefined flux detection point in the motor which is affected by the flux around each rotor bar in the motor as the rotor revolves; generating a synchronization signal once each revolution of the rotor, said synchronization signal occurring when a predefined position on said rotor is closest to said flux detection point; filtering said flux signal to reject signals in a predefined frequency band around and including the frequency at which the rotor bars pass said flux detection point; and synchronously time averaging the output of said filtering step, using said synchronization signal as the synchronization reference for said averaging; whereby statistically significant peaks in the output of said averaging step indicate the presence of a rotor bar fault, and the location of such peaks corresponds to the location of rotor bar faults with respect to said predefined position on said rotor. - View Dependent Claims (22, 23)
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Specification