GB598894A - Improvements relating to the closing control of electric switches - Google Patents

Abstract

598,894. Protective cut - out systems. BRITISH THOMSON-HOUSTON CO., Ltd. July 14, 1944, No. 13512. Convention date, July 14, 1943. [Class 38(v)] A circuit-breaker, adapted to be closed by an electromotive device, such as a solenoid, energised from a variable-voltage source, has means for ensuring complete closure, whilst preventing slamming, by varying the impedance of its operating circuit in accordance with variations in the source-voltage. The closing solenoid 5, is supplied by a battery 7 through contacts 13 of a delayed opening relay 12 controlled by a switch 18, and through a resistance 19 adapted to be short-circuited by contacts 22 of a relay 20 in parallel with the solenoid 5. If the battery voltage is high, relay 20 picks up, preferably with a delay, and resistance 19 is brought into the closing circuit to prevent slamming of the breaker, whilst at low battery-voltages the relay 20 is inoperative and a sufficient current for successful closing is ensured even under heavy-load conditions. In a modification, the relay 20 is brought into circuit by an auxiliary switch on the breaker when the latter has partly closed, Fig 3 (not shown). The relay 20 may alternatively be seriesconnected in the closing circuit, Fig. 2 (not shown).