GB826154A - Improvements in and relating to schrage motors - Google Patents

Abstract

826,154. A.C. commutator motors. BRITISH THOMSON-HOUSTON CO. Ltd. May 17, 1957 [May 18, 1956], No. 15596/56. Class 35. The commutator brushes of one or more phases in a Schrage type machine are transposed to positions displaced by 180 degrees electrical from their normal positions and have either their electrical connections to the stator phase winding or their rockers interchanged. By this means a redistribution of the current at the commutator is achieved, or for small machines, the brush groups may be compressed to cover small commutator arcs so that sufficient room is left for the brushes to be rocked on a single track instead of the usual two separate tracks. In a single-phase form, the brushes D 1 , D 2 connected to stator phase SD are transferred to the opposite side of the commutator and their connections reversed as shown in Figs. 6 and 8, the brushes remaining on the same rockers and in separate tracks. Fig. 4 shows a small four-pole machine in which only half the number of brushes is used by avoiding parallel-connected brushes and using equalizing connections. With the brush groups D 1 , E 1 , F 1 and D 2 , E 2 , F 2 running in the same track, the permissible angle of movement " α " of the rockers R 1 , R 2 is insufficient. By displacing brushes F 1 , F 2 by 180 degrees electrical so that they lie between brushes D 2 , E 2 and D 1 , E 1 on opposite rockers, as shown in Fig. 9, the angle " a " is increased to an acceptable amount for proper control of the motor. It is described how the invention may be applied to machines of higher pole and phase numbers. Specification 25358/11 is referred to.