GB190721174A - Improvements in or relating to Switches, Relays, Measuring Instruments and the like for use in Electric Circuits. - Google Patents

Abstract

21,174. Siemens Bros. Dynamo Works, [Siemens-Schuckertwerke Ges.]. Sept. 24. Switches; cut-outs. - Refers to electric switches and other apparatus operated by a hot wire. A stop is provided to limit the motion of the hot wire after a certain amount of expansion, and then cause it to sag to operate the apparatus. Means are also provided to neutralize the effect on the length of the hot wire due to the alternations of the current, As shown in Fig. 1, the hot wire a is secured at one end to a fixed stud b, passes through a hole in a plate d, and is secured at the other end through a spring c to another fixed stud b<1>. During the first variations in length, the wire is drawn through the hole by the spring c ; but on a certain temperature being reached, a stop e on the wire engages the plate d, and the wire sags and operates a contact k. Fig. 2 shows the arrangement for neutralizing the pulsations in length on an alternating circuit. The expanding element is composed of two similar portions a<1>, a<2> arranged one in each phase m, m' and in line, but insulated from each other by an insulating- coupling i and connected to a stop e and spring c, as in Fig. 1. While the current is increasing in a', it is diminishing in a<2>, and, consequently, the expansion in the wire a<1> is neutralized by the contraction in the wire a<2>, and vice versa. Thus the net result of the phase fluctuations is nil, and it is only the actual variation in the mean square of the current that moves the contact-piece k. Similar arrangements are shown for two- and three-phase currents.