Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1989-08-31
1992-08-04
Stephan, Steven L.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
364481, 364483, H02H 326
Patent
active
051364581
ABSTRACT:
A processor-based tripping system uses a precise three phase current detection circuit using a minimal number of components. A set of current sensors is situated adjacent the current path to sense respective phases of current therein. The current sensors provide respective current signals therefrom which are fed to a ground fault transformer. The ground fault transformer includes input inductors connected to respective ones of the current sensors such that current flowing through each respective current sensor also flows through one of the input inductors. An output inductor in the ground fault transformer is coupled with the input inductors for adding the current signals from the current sensors and for producing an output current signal in the presence of a ground fault. The output current signal is then rectified to provide a rectified signal corresponding to the output current. The processor receives the rectified signal to detect the ground fault in the three phase current path and provides a trip signal to a solenoid to break the current path. The ground fault transformer also includes a test input inductor for receiving an external AC signal to simulate a ground fault.
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Schmeatic of test circuit of Square D-no date.
General Electric Publication GEH-4291.
Crawford Robert J.
Dougherty Thomas M.
Jimenez Jose W.
Square D Company
Stephan Steven L.
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