An Automatic Shunt for Protecting Electric Arc Lamps

8478. Eckstein, A., and Angold, A. E. April 25. Cut-outs.-An arc lamp is protected by an independent electromagnetic cut-out and substitutional resistance. The cut-out may have a vertical non- magnetic tube A, surrounded at the upper end by a coil B in series with the lamp, and at the lower end by a high-resistance coil C connected in parallel thereto. A tubular iron core D slides in the tube, and has arms of wedge section extendi n g laterally through slots on the tube, to make contact with springs G, fixed on a flange F, when the core D descends under the action of gravity or of the high-resistance coil C. A flexible conductor leads to the arms, and the contact with the springs G connects the substitutional resistance in parallel to the lamp when no current is being supplied, or when the lamp offers abnormal resistance. Passage of a normal current through the lamp and the series coil B raises the core D and disconnects the parallel resistance, if the pressure is not excessive. An iron screw I is provided at the upper end of the series coil to adjust its action on the core D. The coils and movable core may be replaced by equivalent electromagnetic devices, and the movable core may be controlled by springs.