GB562066A - Improvements in and relating to thermally operated electric control means for an electric motor - Google Patents

Abstract

562,066. Control of A.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 24, 1942, No. 18302. Convention date, Dec. 31, 1941. [Classes 38 (iii) and 38 (v)] [Also in Group II] A split-phase motor is started and protected against overload by two hot-wire switches. On completion of the supply both motor windings 54, 56, Fig. 6, are energized, after a short interval, the wire 17 expands sufficiently to open contacts 11 and cut out the starting winding 56. On overload the wire 16 expands to open contacts 10. After an interval both wires contract, but contacts 11 are adjusted to close before contacts 10, so that the starting winding is again operative. The two switches are mounted side by side on the same base 9, Fig. 2. Each comprises movable contacts 10 carried by a flexible arm rocking about a pivot 25 and urged to open position by a C- spring 14, but held closed by a wire 16 secured at 28 to the contact carrying arm and at the other end to an adjustable lever 29. A permanent magnet 18, of the alloy described in Specification 423,897, [Group II], gives a snap-action to the contacts. The wire 16 may be made of an alloy of 80 per cent nickel and 20 per cent chromium.