GB1206786A - Improvements in/or relating to electric switches for high currents - Google Patents

Abstract

1,206,786. Heavy current switches; partly magnetic switches. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. 10 Oct., 1967 [11 Oct., 1966], No. 46240/67. Heading H1N and H1S. A quick-break heavy current switch comprises two metal parts 7, 8 separated by a small gap 9 which contains a quantity of conductive liquid 10 connecting the metal parts 7, 8 together, the current path being such that the liquid 10 is subjected to magnetic forces driving it out of the gap and means being provided to prevent this movement until it is desired to open the switch. The movement of the liquid may insert resistance into the circuit (Fig. 2, not shown). In the embodiment of Fig. 9 two cylindrical fixed parts 31, 32 are separated by an insulator 33. A movable cylindrical member 34 is in permanent connection with 31 by a conducting liquid bearing 36 and with 32 by a quantity 38 of conducting liquid trapped between annular surfaces 39 and by a second liquid bearing 40 and a resistor 48. The current loop 51 provides a magnetic force tending to drive the liquid 38 towards, the chamber 45; the abutting surfaces at 39 are maintained in engagement by springs 35 preventing escape of the liquid 38. To open the switch a weight 49 impinges on the member 34 driving it a short distance to the right against springs 35; the liquid 38 escapes into a passage 44 and moves towards chamber 45 progressively inserting the resistance 48 into circuit. The movement of the liquid is assisted by passing a gas, such as hydrogen or helium at 1000-1500‹ C. and a pressure of 100-200 kg.cm.<SP>-2</SP>, through a passage 43. The liquid may be mercury or a sodium-potassium or mercury-indium eutectic. In another embodiment (Figs. 5, 6, not shown) the current normally passes through a stack of metal annuli (19) separated by liquid filled gaps (20); the outer parts of the annuli (19) are divided by insulating rings (21). The liquid is normally maintained in the gaps (20) against the electric forces by an insulating liquid (24) above the surface of the conducting liquid. To open the switch valves (25) are opened permitting the liquid (24) to escape, the electric forces driving the conducting liquid out of the gaps (20) causing the current to follow a much higher resistance path.