GB250570A - Improvements in an automatic quick acting circuit breaking device - Google Patents

Abstract

250,570. Branchu, P. J. April 8, 1925, [Convention date]. Electromagnetic switches; sparking, preventing.-A direct-current switch for opening a circuit rapidly against the action of a spring 9 and completing it again when the current falls off comprises a two-part rubber-wound coil 7 for producing a field in the gap between the polepieces 3 in which the end of the light pivoted contact-member 4 is locked. The extended junction of the two-part winding is provided with a contact 10 and is extended to form an arcing horn 12. The contact 10 is normally engaged by a contact 11 on the contact-member and, when the current in the contact-member becomes excessive, the electrodynamic action between it and the field produces the opening movement. In the open position, the contact-member may engage a subsidiary contact 14 provided with an arc-horn 13, and between the main and auxiliary fixed contacts a resistance 23 may be arranged, as shown in Fig. 4, so that in the " open " position of the switch a reduced current passes through the contact-member, this current being adequate, in the event of a shortcircuit, to maintain the switch open until the short-circuit has been removed. The reclosing movement is retarded by a ratchet-and-pawl device 19, 20 in connection with a train of gear wheels. The heavy current is led to the contactmember by means of rubbing brushes 16. In order that the switch may act more readily with rapidly increasing than with gradually increasing currents, the contact-member is shunted by an inductive resistance 24. The rapid-acting switch may be used in series with an ordinary slowacting switch 25, 28, Fig. 4, in which case the two contact-members are interconnected by the rod 30 so that arm 4 can function independently of arm 25, but if arm 25 is opened it causes the opening of arm 4. With this arrangement, the rapid-moving arm 4 opens first with heavy shortcircuit introducing the resistance 23 and, if the current thus reduced is still excessive, the ordinary switch 25 opens the circuit. The arrangement of interconnected switches shown in Fig. 4 may be used as an automatic starting resistance, as shown in Fig. 5. An ordinary contactor Dn is first closed thereby connecting all the resistances 23b, 23a, 23 in circuit. The closure of Dn removes an interlock from the rapid-acting contact D3 and if the current has fallen off adequately this contactor closes and removes the resistance 23b. Similarly, by the successive action of other rapid-moving contactors the other sections of resistance are removed.