Patent GB-191405467-A (GB)
Title: An Electric Switch Arrangement for a Plurality of Conductors, Machines or Apparatus to be connected with the same Bus Bar and adapted to be Switched in and out, employing a common Safety Resistance.
IPC: G11B7/00
Filed: 1914-03-03
Granted: 1915-06-10
Abstract: 5467. Allgemeine Elektricitats Ges. March 4, 1913, [Convention date]. Sparking, preventing ; protective arrangements. - Relates to switch arrangements for connecting and disconnecting a number of dynamos, transformers, &c. to and from a common bus-bar, of the kind in which the several connexions are switched in and out by main and auxiliary switches in conjunction with a safety resistance common to all the connexions, and consists in positively connecting the main and auxiliary switches, or operating them under control in such a manner as to ensure the correct order of operation both in switching on and switching off, and also when the circuit is automatically switched off in response to excess current Fig. 2 shows a common bus-bar S, a common safety resistance w, and main and auxiliary switches a, b for connecting and disconnecting one conductor, the safety resistance w being utilized in common for other conductors by means of auxiliary busbars S<1>, S<2>. The main switch closes. and opens in three steps, and the auxiliary switch b makes and breaks two connexions respectively to the end and the middle of the resistance, which is cut-out or cut-in in two steps during the full on' and ' full off ' movements of the main switch. With the main switch a fully closed and the auxiliary switch b open as shown, opening of the circuit is effected by moving a hand switch 18 to the right or ' off ' side, closing contacts in an auxiliary circuit containing a battery. The following operations result in order; closure of 'intermediate' relay contacts 21, excitation of closing-coil 13 of auxiliary switch b, closing of this switch and locking by a detent 15, closure of auxiliary contacts 17, closure of relay contacts 23, excitation of unlocking-coil 8 of main switch a, release of this switch from detent 7, and opening by spring or gravity in the order 3, 2, 1. The opening of the main switch acts by means of auxiliary contacts 10 to excite the unlocking coil 16 of the switch b which is thereupon opened by springs, the controlling hand switch 18 having been previously allowed to come back to the mid-position. Automatic opening of the main switch is provided for by an overload relay 19 which acts in the first instance upon the intermediate' relay 21, the subsequent operations taking place as described above for voluntary opening. To close the main switch, the controlling hand switch 18 is moved to the left. The movement serves two purposes. In the first place, it switches in the relay 21 and brings about the closing and locking of the switch b in the manner already described. In the second place, it excites a relay 25 which establishes a path from the auxiliary contacts 17 to the closing-coil 5 of the main switch and brings about the closing of this switch in the order 1, 2, 3, the switch being finally locked full on by the detent 7. Another relay 24 excited simultaneously with the relay 25 breaks the circuits of both relays which return slowly. Before the relay 25 has opened, however, a circuit is established across its contacts through auxiliary contacts 11 on the main switch and the coil 15, thereby tripping open the auxiliary switch b. In a modification, the closing coils and tripping coils of the main and auxiliary switches are all controlled in the proper order by a drum switch rotated by a motor which is started by a push-button. The required order of operations is determined by the disposition of contacts on the drum, and the arrangement is such that the motor stops itself automatically in the full on ' and ' full off ' positions. An overload relay is arranged to start the motor and thus bring about the same sequence of operations as in voluntary opening. In a further modification, instead of employing a separate main switch and auxiliary switch for each line, a common main switch c, Fig. 4, controlling the common safety resistance w is put between the main and auxiliary bus-bars, and each line h is provided with a line-switch d of lighter and cheaper Construction together with an auxiliary switch c. To switch on any line, the corresponding auxiliary switch e is closed first, then the main switch c, which first puts in and then cuts out the resistance, and then the line switch d. The main switch is then opened, first putting in the resistance and then opening circuit through the auxiliary switch e, after which the latter is opened, leaving the line h directly connected by the switch d. To switch off, the auxiliary switch and the main switch are closed in order, and then the line switch, the resistance switch and the auxiliary switch are opened in order. The order of operation is ensured by a motor-driven drum switch with overload relay and push-button control, as described in the previous modifications. The different line switches are preferably provided with interlocks (not shown in the drawing) to guard against their being opened in the currentbearing condition. Electrical interlocking arrangements comprising differential relays with their windings connected in the push-button circuits are described for preventing the switching on or off of more than one line h at a time.