GB191419446A - Protecting Hot-cathode Vacuum Tubes or other Devices havingsimilar characteristics from Overload. - Google Patents

Abstract

19,446. British Thomson-Houston Co., [General Electric Co.]. Sept. 4.. Protective arrangements.-Relates to the protection of vacuum tubes or other discharge devices having unilateral conductivity, such as the hot-cathode tubes described in Specification 15,788/14, [Class 39 (i), Electric lamps, Arc &c.]. In order to guard against the effects of short circuit on a line receiving rectified current from the tubes, or on any other load-circuit in series with them, a device controlling the trip circuit of one or more automatic switches is arranged to respond to increased flow of energy through a tube. In the arrangement shown, two vacuum tubes 1, 2 have their anodes 4, 4' connected to terminals of a transformer 7 and their cathodes 3, 3<1> connected to a work-circuit 9. A battery 11 and resistance 12 are provided for heating the cathodes as described in the Specification referred to above. According to the invention, a circuit-breaker 22 adapted to open the primary circuit 23 has its trip-coil 19 excitable by the operation of an energy relay 17, which comprises a current coil 14 in series with the anode 4 and a potential coil connected across the anode 4 and the cathode 3. The relay responds when an excess-voltage arises coincidently with flow of current through the tube, but not to excess voltage without current. The tube 1 may be provided with a similar protective arrangement. Instead of opening the supply circuit, a resistance may be inserted.