GB1143889A - - Google Patents

Abstract

1,143,889. Vacuum switches; arcing preventing in switches. GENERAL ELECTRIC CO. 6 Dec., 1967 [12 Jan., 1967], No. 55532/67. Heading H1N. [Also in Division H2] A pair of vacuum switches 12, 14 are connected in parallel and operated at the same time by a spring 25 when released by a latch 26, means being provided to prevent release of the latch during the period immediately preceding current zero so that even if the contacts do not separate simultaneously they nevertheless cannot separate on opposite sides of the current zero. The latch 26 is released by a solenoid energized through a controlled rectifier 32; the S.C.R. 32 is connected to a trigger circuit 40 by an overload relay 53. The trigger circuit 40 provides pulses at a fixed point on each A.C. cycle before the peak so that when the relay contacts 54 are closed the S.C.R. is triggered by the next pulse. Inductances (60) (Fig. 1, not shown) are placed in series with each switch 12, 14 to assist current division. In Fig. 3, these inductances are the primary windings 90 of a core balance transformer 75. If due to faulty operation the currents through the two switches are unequal, a relay 93 operates after a delay to actuate an hydraulic reclosing device 70; a further contact 82 prevents reclosing until the vacuum switch contacts reach their fully open position. After several faulty operations a counter 85 disconnects the trigger circuit 40 and the switches remain closed. In a modification (Fig. 4, not shown), the transformer 75 is replaced by two overload relays responsive to the two currents. The two vacuum switches may have a common envelope.