Motor monitoring method and apparatus using high frequency current components
First Claim
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1. A method of monitoring a machine having an electrical current signal which varies during machine operation, comprising the steps of:
- excluding from the electrical current signal all frequencies below a certain threshold corresponding to at least a first harmonic of power line frequency, whereinthe machine is an electric motor having a stator and a rotor, and the electrical current signal is a motor current signal resulting from the operation and condition of at least one of the rotor and stator of the electric motor, the motor current signal including a small high frequency component which modulates a large low frequency component;
correlating at least one characteristic of the electrical current signal to at least one monitored condition; and
correlating changes in magnitude of the at least one characteristic to changes in the monitored condition.
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Abstract
A motor current analysis method and apparatus for monitoring electrical-motor-driven devices. The method and apparatus utilize high frequency portions of the motor current spectra to evaluate the condition of the electric motor and the device driven by the electric motor. The motor current signal produced as a result of an electric motor is monitored and the low frequency components of the signal are removed by a high-pass filter. The signal is then analyzed to determine the condition of the electrical motor and the driven device.
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Citations
19 Claims
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1. A method of monitoring a machine having an electrical current signal which varies during machine operation, comprising the steps of:
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excluding from the electrical current signal all frequencies below a certain threshold corresponding to at least a first harmonic of power line frequency, wherein the machine is an electric motor having a stator and a rotor, and the electrical current signal is a motor current signal resulting from the operation and condition of at least one of the rotor and stator of the electric motor, the motor current signal including a small high frequency component which modulates a large low frequency component; correlating at least one characteristic of the electrical current signal to at least one monitored condition; and correlating changes in magnitude of the at least one characteristic to changes in the monitored condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of monitoring an electric motor-driven machine comprising the steps of:
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producing a power line current signal which varies during machine operation; excluding from the current signal all frequencies below a threshold corresponding to at least a first harmonic of line frequency; correlating at least one characteristic of the current signal to at least one monitored condition; and correlating changes in magnitude of the at least one characteristic to changes in the monitored condition.
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12. An apparatus for monitoring a machine having an electrical current signal which varies during machine operation, comprising:
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means for excluding from the electrical current signal all frequencies below a threshold corresponding to at least a first harmonic of power line frequency, wherein the electrical current signal is a motor current signal resulting from the operation of the machine, the motor current signal including a small high frequency component which modulates a large low frequency component; means for correlating at least one characteristic of the electrical current signal to at least one monitored condition; and means for correlating changes in magnitude of the at least one characteristic to changes in the monitored condition. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification