GB816401A - Improvements in and relating to electrical induction relays - Google Patents

Abstract

816,401. Inductors; induction motors. ENGLISH ELECTRIC CO. Ltd. June 4,1956 [June 3, 1955], No. 15966/55. Classes 35 and 38 (2). [Also in Group XXXVII] A relay intended to respond against a mechanical restraint when the impedance of a line falls below a certain value and having two separate shaded-pole magnet systems acting in opposition upon an electro-conductive armature, one magnet system being energized in accordance with the line current and the other in accordance with the line voltage-this latter system acting in the restraining sense, is provided with a saturable inductance to prevent a lowering of the response value of the line impedance at low values of line voltage. The saturable inductance may be either in effective series connection with the voltage winding or in effective parallel connection with the current winding; alternatively, the relay may have both these inductances. As shown, Fig. 2, an E- shaped voltage core 10 energized by coils 11 has an outer lamination 12 of high permeability and a further lamination 13 of high permeability forming a flux leakage path. At high values of line voltage the laminations 12, 13 are saturated but at low voltages they are not saturated and a greater proportion of the flux passes therethrough and hence the working proportion of the flux is reduced and the magnet 10 offers less restraint. The current core 15, Fig. 4, energized by coils 16, has a lamination 14 of high permeability which saturates at high voltages and thus at low voltages when the lamination 14 is not saturated the working flux, which flows through 14, 15, is proportionally increased. To provide exact adjustment of the relay characteristic a few turns of copper wire may surround the high-permeability laminations to provide an eddy current path, these turns being connected to a variable resistor; alternatively, the turns may be shorted successively by twisting their ends until the adjustment is obtained.