Patent GB-190820268-A (GB)
Title: Improvements in or relating to Overload Circuit Breakers.
Filed: 1908-09-26
Granted: 1909-07-22
Abstract: 20,268. Siemens Bros. Dynamo Works, [Siemens-Schuckertwerke Ges.]. Sept. 26. Switches; cut-outs.-Overload circuit breakers, for use with sectional conductors for traction systems, for isolating a section if a fault occurs, consist of a single main switch, interposed between adjoining sections, which is opened by the overload and re-set by a device dependent on the conjoint action of both sections when restored to their normal potential, so that the act of restoring the section to its normal state re-sets the circuitbreaker. In Fig. 1, the two sectional conductors a, b, which are fed by feeders c, d, through cut-outs e, f, are connected to contact springs h., i. The circuitbreaker k is provided with a contact bridge l, for the contact springs h, i, and with a bridge m to bridge the contacts n, o forming the re-setting switch. In circuit with the main conductor a is a solenoid p, which, when an excessive current flows, opens the main switch h, l, i ; a solenoid q, connected to main conductors a, b tends to re-set it. A point q<1> at the middle of the solenoid q is connected to the contact o, while the contact n is connected to the opposite pole of the generator to that to which the conductors a, b are connected. Spring latches s, t are held out of engagement with the cut-out by means of solenoids w, x connected between sections a, b and the return wire r. If an overload occurs in either section, for example section b, a heavy current passes through the solenoid p and operates the cut-out, opening the circuit h, i and closing the re-setting circuit, n, o. The same overload will actuate the feeder cut-out f, and render the wire b dead, in consequence of which the solenoid x is de-energized and the latch t engages the cut-out and prevents the re-setting coil from acting. A current passes from the section a through the left half of the re-setting solenoid q, through contacts o, m, n to the return r, but the cut-out will not re-set until the wire b is connected again to the circuit; the solenoid x is then re-energized, releasing the latch t, s and allowing the cut-out to return. In order that the lever, on being pulled by the solenoid, shall complete its travel so that it may be engaged by one of the latches, a delaying-device may be used ; for example, a switch may be inserted in the lead y, normally closed by a spring but opened by an electro-magnet, so long as a current flows in the wire z. In a modifled form, the spring latches s, t are dispensed with ; a simple-wound re-setting solenoid is connected between one of the sections and the return, and is prevented from acting by placing in circuit with it an electro-magnetic switch that closes only when the other section is energized. In the form shown in Fig. 4, the oveloid coil p<1> trips a latch 7 and allows the spring 6 to pull over the cut-out. The re-setting solenoid is formed in two parts 4, 5, which are so wound that it will only act when both parts are energized, i.e. when both sections a, b are in circuit. On being pulled over, the latch 7 re-engages with the lever k.