Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1977-09-06
1979-07-17
Salce, Patrick R.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
361 98, H02H 308
Patent
active
041617614
ABSTRACT:
The minimum instantaneous voltage output of a phase resistor connected to receive the rectified phase and neutral currents of three wye-connected current transformers, magnetically coupled to respective phase conductors of a three phase electric power circuit, is proportional to the peak current of the phase conductor carrying the center magnitude phase current. A voltage proportional to this minimum instantaneous voltage is measured and stored by a capacitor each cycle. The peak instantaneous voltage output of a ground resistor connected to receive the full wave rectified output of three, parallel-connected current transformers, also coupled to respective phase conductors of the power circuit, is proportional to the peak ground current of the electric power circuit. A voltage proportional to the voltage output of the ground resistor is applied to the base of a NPN transistor, and the voltage stored by the capacitor is applied to the emitter of this transistor, to turn on this transistor every time the peak ground current exceeds a preselected percentage of the center magnitude phase current. The momentary turnon of this transistor at least once every current cycle activates a timing circuit, which after a predetermined time, initiates tripping of a circuit interrupter.
REFERENCES:
patent: 3345539 (1967-10-01), Ashenden et al.
patent: 3434011 (1969-03-01), Zocholl
patent: 3689801 (1972-09-01), Engel et al.
patent: 3956670 (1976-05-01), Shimp et al.
patent: 4027203 (1977-05-01), Moran et al.
patent: 4060844 (1977-11-01), Davis et al.
Gealow Jon C.
LaPorte Ronald J.
McDonald Thomas E.
McGraw-Edison Company
Salce Patrick R.
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