Patent GB-209412-A (GB)
Title: Improvements in electrical protective systems
IPC: H02H3/07
Filed: 1923-12-31
Abstract: 209,412. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Travers, H. A.). Jan. 5, 1923, [Convention date]. Protective arrangements.-In an automati. cally-reclosing circuit-breaker system, the reclosure is effected a predetermined number of times in succession at predetermined time intervals by means of a small electric motor driving a contact drum having timing contacts and limit contacts for the motor, and, if the abnormal conditions are removed before the last reclosure, the circuit-breaker remains closed and the motordriven timing and limit switch is driven reversely to the original position, whereas, if the overload &c. persists, the circuit-breaker is finally opened and can only be re-closed bv hand. The circuitbreaker 3 having auxiliary front and back contacts, as shown, is located in the protected circuit 2 and is brought to the closed position against the action of a spring by energization of a coil 12 and locked in that position by a latch until released by the overload trip-coil 4 energized from a current transformer 5, or by an auxiliary tripcoil 6 the current in which is under manual control. The coil 4 is in series with the operating coil of a lock-out relay 46 which, in the event of very heavy overload &c., opens the control circuits at 45 and prevents operation of the automatic re-closing means. The system is under manual control by a switch 14 the contact 41 of which closes the relay 11, thereby completing the re-closing circuit from an auxiliary source. The switch 14 has additional contacts 42, 43 interconnected so that when one is closed the other is open; 42 controls the auxiliary trip coil 6, and 43 controls the supply circuit for the automatic re-closing operation. The re-closing control relay 13 shown in the closed position is opened due to momentary energization of its coil 36 when the circuit-breaker is closed. When, on overload &c., the circuit-breaker is tripped, the series motor 8 is energized through the contacts 18 together with its field winding 16 and the drum 9 is slowly driven downwards, through gearing. The drum carries a contact 24 co-operating with fixed contacts 20 21, 22, to limit the movement of the motor, and segments 31, 32. 33 and 28, 29, 30 to determine the timed re-closure. In the first part of the drum movement, the segment 28 bridges fixed contacts 25, 26 and energizes the latch ooil 37, thereby allowing the relay 13 to close again. After a predetermined interval, the segment 31 bridges fixed contacts 26, 27 and completes the re-closing circuit for relay 11 through 35, 14, and 45. If, on re-closure, the overload persists, the circuit-breaker opens and, after a predetermined interval which may be longer than the previous one. it is again automatically re-closed. This continues a third time, after which, with the circuit-breaker open, the limit contact 24 passes off the fixed contact 22 and the, motor stops. If the overload &c. is removed at anv time before this final stage is reached, the circuit-breaker remains closed and, through the contacts 17, the motor is supplied together with its alternative field winding 15, and, in consequence, rotates the drum in the reverse direction to the original position where it is stopped by uncovering the contact 20. A push-switch 50 is provided for re-setting the lock-out switch 46 electromagnetically.