GB369730A - Improvements in and relating to the control of electric motors - Google Patents

Abstract

369,730. Control of A.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Hamm, C. L. ; 221, 1st Street, Pittsfield, Massachusetts, U.S.A.) Feb. 28, 1931. No. 6325. Convention date, Feb. 28, 1930. [Class 38 (iii).] A split phase induction motor employing capacity in the auxiliary phase has a main primary winding 11 with different terminals for connection to sources of supply of different voltages, and a starting winding 12 connected to the main winding in series with a capacity, the main winding serving as an adjustable autotransformer to vary the relative magnitudes of the voltages impressed on the main and starting windings. Speed control may be effected by connecting the mains to different tapping points on the winding 11. If the auxiliary winding circuit is to remain connected during normal running for power factor correction, the amount of capacity may be varied by employing two condensers connected in parallel at starting and in series during normal running. The necessary change may be effected automatically as shown in Fig. 3. A relay 23 having a coil 25 connected across the starting winding 12 through a resistance 26 is energized at sufficiently high speed to close the circuit of a coil 27 of a relay 24 to connect the condensers 20, 21 in series. In the event of an overload causing a drop in speed, the relays operate to re-connect the condensers in parallel. If close control is unnecessary, a single relay may be used.