GB769752A - Improvements in or relating to arrangements for limiting overload currents - Google Patents

Abstract

769,752. Protective cut-out arrangements; electrically released switches. FKG F. KESSELRING GERATEBAU AKT.-GES. April 27, 1955 [April 29, 1954], No. 12168/55. Addition to 748,532. Class 38(5) In a protective arrangement having a current limiting fuse 23 of low rating and a very rapidly acting switch shunting the fuse, the discharge of a condenser 8 fuses a wire 91 to cause the evaporation of an insulating medium 92, e.g. oil, fat, water or glycol, so that the pressure produced acts on a diaphragm 93 to impart a thrust to an insulating rod 10. The rod 10 acts on the movable contact 21 to fracture a latch 22 of impregnated paper or ceramic or glass-like material and to assist in accelerating the contact which is opened under the bias of a spring 24. The arrangement may be used for ordinary overload protection as in the main patent, but in the arrangement shown protects a contact rectifier 4 against excessive reverse current when a "backfire" occurs. In that event, the current impulse produced in the secondary winding 52 of a premagnetized transformer 5 breaks down a multiple electrode pre-ionized spark gap 7 to permit the condenser 8 to discharge through the wire 91, the condenser being normally kept charged by a transformer 82 and rectifier 81.