Importance

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Abstract

A method and apparatus for detecting a stator winding fault in an induction motor includes sampling instantaneous signals from the motor and then deriving sequence components of at least some of the instantaneous signals using a power decomposition technique (PDT), one of the sequence components being a total negative sequence current component. In addition, the method includes calculating an expected negative sequence current based on at least some of the sequence components. Thereafter, the method subtracts the expected negative sequence current from the total negative sequence current to determine a fault negative sequence current, wherein the fault negative sequence current is indicative of the fault. More preferably, the method additionally includes calculating an intrinsic motor negative sequence current based on at least some of the sequence components, and subtracting the intrinsic motor negative sequence current from the fault negative sequence current generated as described above to determine a modified fault negative sequence current. Notably, the method and apparatus are capable of detecting faults that cause a modified fault negative sequence current as low as approximately 0.2% of the full load current.

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First Claim