GB1451958A - Electrical switches - Google Patents

Abstract

1451958 Switch contacts; heavy current switches M T E COMPONENTS Ltd and N H OLLEY 21 Feb 1974 [3 May 1973] 21099/73 Heading H1N A switch, wherein electromagnetic force normally urging the contacts closed is removed as the contacts move to open, comprises conductive means 48, 44 supporting the fixed contact 42 such that current flowing therein when the contacts are closed, Fig. 3, generates an electromagnetic field urging the fixed contact 42 against the moving contact 40, and when the contacts are broken the current path is mechanically altered, Fig. 4, in such a manner as to substantially remove the said electro magnetic field. As shown the contact-carrying member 44 is hinged at 46 to the conductive member 48 which is mounted on insulation 51 A hole 60 is large enough to keep spring 56 insulated from member 48. A neck-like portion of member 44 passes through an aperture 52, and terminates in a crosspiece 54. When moving contact 40 engages contact 42 current flows as indicated in Fig. 3 and electrodynamic force acts on contact arm 44 to urge the contacts together. When contacts 40, 42 open, spring 56 urges the crosspiece 54 into contact with member 48, Fig. 4, thereby short-circuiting the current loop of Fig. 3 and avoiding deleterious effect of the electromagnetic field thereof on the arc between contacts 42 and 40. A plurality of moving contacts 40 may be mounted on a channelshaped member (10), Fig. 1 (not shown) arranged for linear movement upon rotation of a shaft (12) to open and close an isolator switch. Rotation of shaft (12) moves two bars (20, 22) in opposite directions to cam the member (10) by means of a pair of pins (28, 30) thereon which engage in slots (24, 24', 26, 26') in the bars (20, 22). Six sets of contacts as shown in Figs. 3 and 4 may be fitted to provide a double-break three-phase isolation switch. Each pair of movable contacts on member (10) may be connected directly or by respective fuse links to provide moving contact bridges.