GB806983A - Improvements relating to controllers for split-phase electric motors - Google Patents

Abstract

806,983. Electromagnetic switches; control of A.C. motors. GENERAL MOTORS Ltd. June 21, 1957 [July 10, 1956], No. 21340/56. Classes 38 (5) and 38 (3). A split-phase motor starting relay has its solenoid coil 53 in series with the main motor winding 74, a protective bi-metal strip 4 and heater 19 controlling contacts 3, 5. When energized, the solenoid attracts an armature 42, the weight of which normally holds a strip spring 29 against its bias, so that contacts 46, 47 can close to energize the starting winding 85. In its upward movement the armature engages the bent end 36 of a resilient member 31 (Fig. 2) and closes contacts 25, 30 to short-out part of the coil 53. The reduction of the attractive force on the armature and the resilience of the member 31 cause the armature to move downward and as the starting current in the motor winding also falls the armature drops to open the contacts 46, 47. The contacts 25, 30 do not open immediately, since the main winding current passes along one limb 24a of a bi-metallic member 24 carrying the contact 25 so that the heating of the member 24 causes the contact 25 initially to follow the contact 31. An adjustable stop-screw 43 limits the movement of the armature 42 and spring 29. In a modification (Fig. 4) the contacts 25, 30 are omitted and the armature 42, in its upper position strikes a rivet 36A carried on a resilient bimetallic arm 31A carrying the total current and which is bent down on heating to assist in restoring the armature.