Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Patent
1997-08-18
1999-04-13
Medley, Sally C.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
361 78, H02H 300
Patent
active
058943927
ABSTRACT:
A power distribution unit for supplying temporary branch power has a 240-250 VAC input with input power line conductors L1 and L2, a neutral conductor N, and a ground conductor G. A supervisory circuit checks that the 240-250 VAC input is properly connected to the power distribution unit by requiring that the input voltage exceeds a supervisory circuit threshold voltage substantially greater than 120-125 volts. When that occurs, a contactor is enabled by the supervisory circuit to close first and second contacts therein to pass the 240-250 VAC on lines L1 and L2 therethrough to a 240-250 VAC ground fault interrupter protected circuit breaker outlet. A plurality of 120-125 VAC GFI module outlets are connected across either one of lines L1 and L2 at the output of the supervisory circuit and the neutral conductor N which bypasses the contactor. The supervisory circuit includes a diode bridge circuit connected across power line conductors L1 and L2 to convert a 240-250 VAC input to 240-250 VDC. A voltage threshold zener diode is connected in series with first and second relays across the 240-250 VDC, such that the zener diode ensures that the voltage required to operate the first and second relays is substantially greater than 120-125 VDC. The first relay operates contacts to activate the contactor, and the second relay operates contacts to bypass the neutral conductor N around the contactor.
REFERENCES:
patent: 3783354 (1974-01-01), Fletcher et al.
patent: 4532569 (1985-07-01), Salcedo
patent: 5418678 (1995-05-01), McDonald
patent: 5786971 (1998-07-01), Chan et al.
"An easy guide to the Hubbell Spider", pp. 1-28.
'Hubbell Incorporated
Medley Sally C.
Presson Jerry M.
Roch William C.
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