Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Patent
1988-12-19
1990-01-16
Thompson, Gregory D.
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
H05K 700
Patent
active
048947482
ABSTRACT:
A control terminal for use in hazardous environments, or in environments which are deleterious to electronic devices is disclosed. The terminal is housed in an enclosure which is purged with clean dry air or inert gas and is maintained at a slight positive internal pressure to prevent entry of the outside atmosphere. All electrical connections and purge controls which are active prior to completion of the purge are housed in internal and external explosion proof boxes, except for the explosion-proof flow switch which controls the purging air flow. After purge, the slightly positive internal enclosure pressure is controlled by a gas demand switch which operates a valve to admit air whenever internal pressure drops below the gas demand switch set-point. A low pressure cut out switch opens and interrupts terminal power whenever internal pressure drops to the low pressure cut out switch set point which is barely above one atmosphere, absolute. Overtemperature protection is provided by temperature sensors which activate purge air flow to purge warm air from the enclosure or to interrupt terminal power when the purge air cooling rate is less than the terminal operation heating rate.
REFERENCES:
patent: 1453083 (1923-04-01), Schuler
patent: 2250977 (1941-07-01), Walker
patent: 2307612 (1943-01-01), Westendorp
patent: 2943134 (1960-06-01), Liao et al.
patent: 3275893 (1966-09-01), Phillips et al.
patent: 3281521 (1966-10-01), Wilson
patent: 4685018 (1987-08-01), Tada et al.
Palermo Robert F.
Thompson Gregory D.
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