GB191111350A - Improvements in and relating to Controlling Means for Electric Circuits. - Google Patents

Abstract

11,350. British Thomson-Houston Co., [General Electric Co.]. May 10. Electro - mag - netic switches.- An electro - magnetic switch is mechanically biassed against gravity to the open position, and the winding produces fluxes through two parallel paths. One flux releases the mechanical biassing means and substitutes magnetic means, and the other flux assists gravity to close the switch when the current falls to a predetermined value. The winding 10, Fig. 1, has a fixed magnet frame 17 and a movable core 11, which carries a brass rod 14 passing through an iron plate 12. This plate enters recesses in the pole-pieces 18, 19 and rests on brass spacers 23, 25 and is secured by screws. Iron lugs 13 on the plate 12 support the pivot 33 of the switch arm 26, which is of iron and of considerable mass at the end which acts as armature to the pole 19. The other end of less mass acts as armature to the pole 18, and a pin 35 on the arm engages a brass lug or disk 34 on the rod 14, so that the switch is held in open position. The air-gap 38 between the switch arm and the pole-piece 18 can be adjusted by means of the screw 36. When a large current flows in the winding 10, the core 11 is raised, thereby releasing the pin 35 and removing the mechanical opening bias, but the switch remains held open by the flux in the air-gap 38, which is shunted by a nearly closed magnetic path through the plate 12 and frame 17. As the current decreases, the flux across the gap 38 decreases, until it is insufficient to hold the switch arm, which then moves to its closed position under the influence of gravity and the flux in the gap 39. When the current falls to a negligible value, the core drops and opens the switch with a hammer blow. In a modification, Fig. 6, the core 41 is fixed, and the plate 43 carries an iron switch arm 53 in lugs 51. The end 56, Fig. 7, of the arm forms the armature for the polepiece 47. The weight of the arm tends to close the switch, but this is prevented by a lever 57 which carries a brass pin 58 passing through a slot 59 in the switch arm. The lever 57 is forced into the position shown in Fig. 6 by a spring 56<1>. When a large current flows, the lever 57 is pulled down by the pole-piece 47, and this removes the mechanical bias from the switch arm, which does not move however as it is held by the flux across the gap 61. When the current falls to a sufficiently low value, the flux across the gap 61 fails to hold the switch, which is then closed by gravity and the flux across the gap 62.