Electric lamp and discharge devices: systems – With automatic shunt and/or cutout
Patent
1988-11-21
1989-12-26
Britton, Howard W.
Electric lamp and discharge devices: systems
With automatic shunt and/or cutout
315244, 315224, 315306, 315309, H05B 3700
Patent
active
048900397
ABSTRACT:
Subject invention relates to a fluorescent lamp ballast that is intended for safe and cost-effective use in lighting systems wherein the power to the various lighting fixtures is provided from a central source of relatively high frequency (Ex: 30 kHz) AC voltage. The ballast consists of a resonant series-circuit of an inductor and a capacitor--with the fluorescent lamp connected in parallel with the capacitor. Due to series-resonant action, if the lamp should happen to be non-connected or non-functional, and if proper precautions are not taken, the magnitude of the voltage developed across the capacitor may become so large as to cause damage to the circuit components and/or even to the source. To prevent such circuit damage, yet providing for a lamp starting voltage of suitably large magnitude and for an adequately long time, a Varistor voltage-limiting means is connected in parallel with the capacitor and a thermally actuated circuit breaker is connected in thermal contact with the Varistor. When actuated, the circuit breaker stops the series-resonant action. Under normal circumstances, when starting the fluorescent lamp, the magnitude of the voltage developed across the capacitor will be limited by the Varistor; which, during the brief period it takes for the lamp to ignite, will not become hot enough to cause the circuit breaker to actuate. If the lamp is non-connected or non-functional, however, the Varistor will provide voltage limitation for a longer time; and, after a few seconds, it will become hot enough to cause actuation of the circuit breaker. Once actuated, the circuit breaker remains actuated until power is removed from the ballast input.
REFERENCES:
patent: 3710177 (1973-01-01), Ward
patent: 4370600 (1983-01-01), Zansky
patent: 4398126 (1983-08-01), Zuchtriegel
patent: 4406976 (1983-09-01), Wisbey et al.
patent: 4461980 (1984-07-01), Nilssen
Britton Howard W.
Powell Mark R.
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