Detection of arcing faults in polyphase electric machines
First Claim
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1. An electric machine having a polyphase winding with an arcing detector, comprising:
- a high-frequency current transformer disposed about each phase lead of said polyphase machine, said current transformer outputting a current signal proportionate to the magnitude of radio frequency current flowing in its associated phase lead;
means connected to the output of each of said current transformers for converting said proportionate current signal to a direct-current voltage value; and
means for individually measuring the magnitude of said direct-current voltage value for each phase winding of said polyphase electric machine.
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Abstract
A method is provided for detecting the existence of arcing faults in the phase windings of a polyphase electric machine and for simultaneously identifying the specific phase winding in which the arcing fault exists. Arcing faults in phase windings of electric machines cause high frequency currents to flow through all phase windings of the machine with a drastically higher magnitude in the phase winding in which the arcing fault exists. These currents can thus be measured to determine the existence of the arcing fault and selectively determine which phase is affected.
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Citations
11 Claims
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1. An electric machine having a polyphase winding with an arcing detector, comprising:
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a high-frequency current transformer disposed about each phase lead of said polyphase machine, said current transformer outputting a current signal proportionate to the magnitude of radio frequency current flowing in its associated phase lead; means connected to the output of each of said current transformers for converting said proportionate current signal to a direct-current voltage value; and means for individually measuring the magnitude of said direct-current voltage value for each phase winding of said polyphase electric machine. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for selectively determining the existence of an arcing fault in one phase winding of a polyphase electric machine, said method comprising:
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monitoring individually the magnitude of radio frequency current in each phase winding of said polyphase electric machine; comparing the magnitude of said radio frequency current flowing in each of said phase windings to an acceptable threshold value in order to determine whether an arcing fault exists in the specific phase winding indicated by a radio frequency current magnitude greater than that flowing in the other phase windings of said polyphase electric machine. - View Dependent Claims (8, 9, 10, 11)
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Specification