GB546266A - Improvements in and relating to electromagnetic switches, particularly for use as starting relays for alternating current motors - Google Patents

Abstract

546,266. Electromagnetic switches. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). Nov. 28, 1941, No. 15338, [Class 38 (v)] An electromagnetic switch specially adapted for use as a starting relay with split-phase A.C. motors having a running winding 45 and a starting winding 46, has normally closed contacts 23, 24 which remain closed when a switch 49 is operated and the large " starting " current flows through the operating winding 13 of the electromagnetic switch, the contacts only opening when the winding 13 is partially de-energized due to the motor speeding up. When finally the switch 49 is opened, the contacts again close and the switch is restored to its original position. The magnet 13 has a pole 14 which attracts an armature 17 mounted on a cantilever spring 19 and carrying the contact 23. The co-operating contact 24 is mounted on a spring 25 and tends always to engage the contact 23. When the. armature is attracted both contacts move down and the spring 25 is held against return by the shoulder 39 of a latch which is biased to move in a clockwise direction about a pivot 36. Partial de-energization 'causes the armature to move back part way, the contact 23 moving away from the contact 24. Full de-energization causes the armature to return to its original position and a pin 41 carried by the armature moves the latch so that this releases the spring 25 and the contacts 23, 24 re-engage.