GB396237A - Improvements in or relating to electric switches - Google Patents

Abstract

396,237. Protective cut-out arrangements and automatic circuit-breakers. KRATZ, H., 62, Baerler Strasse, Moers, Germany. Sept. 15, 1932, No. 25732. Convention date, Sept. 15; 1931. [Class 38 (v).] A circuit-breaker for use with electric motors, transformers, &c. has the electromagnetic or thermal tripping devices arranged to be operable by 'two coils one of which is connected with its one end to the neutral point of the apparatus and the second with its one end to the body of the apparatus, the other ends of both coils being connected to the neutral point of the supply. As shown in Fig. 1 the circuit-breaker 5 controlling the connection of the motor 6 to the three-phase supply 2, 3, 4 is operated by coils 8a, 8b the former of which is connected between the neutral wire 1 of the supply and the neutral point 6a of the motor windings and the other of which is connected between the supply neutral wire and the motor frame. The circuit of the coil 8b includes an adjustable resistance 12 which limits the current in this winding so that release of the circuit-breaker will not be effected by the small current which normally flows between the two neutral points. When either of the coils 8 are, however, sufficiently energized the consequent attraction of the armature 10 causes the release of the switch 5. The resistance 12 may be. varied in value to vary the sensitivity of the cut-out. In the electromagnetic cut-out shown in Fig. 2 the coils are wound concentrically around the armature 10 and on sufficient energization of either or both coils the armature is attracted to uncouple the switch drum from the operating member and the switch drum is rotated to break circuit under the action of the spring 25. In a modification, Fig. 4 (not shown) a fine adjustment of the cut-out is effected by screwed adjustment of the position of the core within the operating coils. The coils may be surrounded by a divided magnetic housing to produce a magnetic blow-out action. In the thermal type of circuit-breaker each coil may act on a thermal trip member.