GB690254A - Electric motor - Google Patents

Abstract

690,254. Electric motors. SOC PARVEX. May 16, 1951 [July 12, 1950], No. 11412/51. Class 35. In a universal motor the commutator brushes are displaced from the neutral axis, so that the armature reaction serves to excite the field poles, these being left unwound. In the two-pole machine shown in Fig. 1, and having an unwound stator field 10, the brushes 23, 24 are displaced by about 45 degrees from the neutral axis so that those armature coils in the interpolar space serve to generate the working flux while the coils opposite the poles produce the working torque. The direction of rotation is reversed by means of a change-over switch 43 which connects the supply 40, 41 to an alternative pair of brushes 35, 36 which are displaced from the neutral axis in the opposite direction. Commutating poles 44, 45 and 49, 50 corresponding to the brush pairs may be energized by connection in series with the armature or, in A.C. machines by current induced in short circuited windings. A fourpole, wave-wound motor is described. In a further modification, shown in Fig. 4, the stator 100 carries the distributed winding which is connected to a stationary commutator 106, while the rotor 101 carries rotary brushes 108, 109 fed through slip-rings. As before, the brush axis is displaced by an angle b from the neutral axis 122, 123 of the unwound member. A second pair of brushes displaced in the opposite direction and producng reversed rotation may be added.