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Monitoring synchronization of a motor using stator current measurements

  • US 10,054,641 B2
  • Filed: 09/20/2013
  • Issued: 08/21/2018
  • Est. Priority Date: 09/20/2013
  • Status: Active Grant
First Claim
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1. An intelligent electronic device (“

  • IED”

    ) for monitoring synchronization of a motor using stator currents, comprising;

    an input in communication with current transformers (“

    CTs”

    ) each in electrical communication with a phase of current supplied to stator windings of the motor;

    a processor in communication with the input, receiving current data points corresponding with the current supplied to the stator windings; and

    ,a non-transitory computer-readable storage medium in communication with the processor, the non-transitory computer-readable storage medium comprising;

    a synchronization module configured tocalculate a root-mean squared value from the current data points for each phase of current supplied to the stator windings of the motor;

    sum the root-mean squared values from each phase;

    calculate a DC component from the sum of the root-mean squared values from each phase;

    calculate representative current values by subtracting the DC component from the sum of the root-mean squared values; and

    calculate using the representative current, and without using values from a voltage across a discharge resistor of field windings of the motor, an estimate of synchronization ofa rotational frequency of the rotora rotational frequency of an electric field of the stator windings of the motor; and

    control a configuration of the motor based on the estimate of synchronization by opening a switch to disconnect the discharge resistor from the field windings of the motor when the estimate of synchronization has reached a predetermined threshold.

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