GB546582A - Improvements in or relating to electromagnetic switches - Google Patents

Abstract

546,582. Electromagnetic switches. IGRANIC ELECTRIC CO., Ltd. July 29, 1941, No. 9635. Convention date, Aug. 1, 1940, [Class 38 (v)] An electromagnetic switch, which may control a welding circuit 2 and is adapted to open and close at predetermined points of an A.C. cycle, has a core 1a, a main winding 1h, a secondary " shading " winding lj embracing a portion only of the flux, and contacts 3b, 3d adapted to short circuit the winding lj and also to connect the winding 1h across the A.C. lines L 1 , L 2 . The winding 1h may form part of a winding 1g which is in series with a resistance 4, variable reactor 5 and variable condenser 6 to form a closed oscillating circuit ; and the armature 1b, 1d may be associated with a holding magnet 1c having main and secondary coils lk, 1l arranged similarly to those on the magnet 1a. In operation, closure of a push-button switch 7 completes at 3d the circuit of operating coil 1h and breaks at 3c the circuit of holding coil 1k. The shading coil 1l is simultaneously open-circuited, and the actual movement of the armature to close contacts 1f will occur when the A.C. in the holding coil is passing through the zero of its cycle and the arc at the contact 3c is therefore broken. To open the contacts 1f, push-button 7 is released whereupon a similar action occurs, coil 1h now, however, holding the armature closed against the influence of gravity &c. till its current passes throuh the zero point. The exact moment for this is delayed for an adjustable time owing to the presence of the oscillatory circuit 1g, 4, 5, 6, the current in which persists after the contacts 3d have opened and .the arc there interrupted. This oscillatory current must therefore pass through the zero of its cycle before the armature is released.