Electric lamp failure indicator circuit
First Claim
1. A device for indicating an electric lamp failure, comprisingi. a core of magnetic material in the form of a closed loop,ii. a first winding on the core forming an electrical circuit with the lamp allowing electric current to flow through said lamp while said lamp is operable, said current being either induced by said core when said lamp is unenergized or supplied by a source of direct electric current for energizing said lamp when said lamp is energized, the number of turns on the first winding being such as to result in magnetic saturation of the core when the lamp is energized,iii. a second winding on the core in circuit with an electrical circuit for generating electric current pulses in the second winding whereby variations in magnetic flux density are induced in the core, andiv. a third winding on the core forming an electrical circuit capable of detecting the amplitude of a voltage or current induced in the third winding as a result of a change in amplitude of the said variations in flux density in the core occasioned by failure of the lamp.
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Abstract
A core of magnetic material in the shape of a closed loop has three windings thereon. The first winding forms a circuit with a lamp to be monitored. As long as the lamp'"'"'s filament is intact, whether or not the lamp is energized, this circuit can conduct current. The second winding is connected to a pulse generator to induce variations in the magnetic flux in the core. The third winding detects these variations in flux and a detection circuit connected to the third winding produces an indication if the variations are greater than a predetermined threshold. If the lamp is energized, the current in the first winding causes the core to be saturated with magnetic flux and thus the induced flux variations are below the detection threshold. If the lamp is unenergized, but intact, the current pulses in the second winding induce counter-pulses in the first winding which counteract the effect of the pulses in the second winding and thus the induced flux changes are below the detection threshold. If the lamp filament is broken, the pulses in the second winding will produce a sufficient change in flux in the core to be detected. Thus a defective lamp is detected whether or not it is energized. A second embodiment monitors two lamps with one core.
22 Citations
6 Claims
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1. A device for indicating an electric lamp failure, comprising
i. a core of magnetic material in the form of a closed loop, ii. a first winding on the core forming an electrical circuit with the lamp allowing electric current to flow through said lamp while said lamp is operable, said current being either induced by said core when said lamp is unenergized or supplied by a source of direct electric current for energizing said lamp when said lamp is energized, the number of turns on the first winding being such as to result in magnetic saturation of the core when the lamp is energized, iii. a second winding on the core in circuit with an electrical circuit for generating electric current pulses in the second winding whereby variations in magnetic flux density are induced in the core, and iv. a third winding on the core forming an electrical circuit capable of detecting the amplitude of a voltage or current induced in the third winding as a result of a change in amplitude of the said variations in flux density in the core occasioned by failure of the lamp.
Specification