GB275264A - Improvements in and relating to alternating current motors - Google Patents

Abstract

275,264. Maatschappij tot Vervaardiging van Snijmachines Volgens van Berkel's Patent en van Andere Werktuigen, (Assignees of Rieuks, W.). July 30, 1926, [Convention date]. Motors. controlling.-In an alternating current induction motor adapted to have its pole number changed by a reversal of current in part of the stator winding, an additional winding is provided in the stator slots which is connected in series with the main winding when the motor operates on the largest pole number, so that with a constant supply voltage the same torque is produced on each pole number. In the form shown. C - - F represent the coils of one phase of the main winding, and G, H, J, K the coils of the additional winding. In order tc obtain a sinusoidal field distribution for a 4-pole operation, the number of conductors per slot of the main winding decreases from a maximum in the outside slots 1. 8, 9, 16, &c. to a minimum in slots 3, 6, 11, 14. &c., whereas slots 4, 5, 12, 13, &c. carry no main coil conductors. To maintain the sinusoidal field distribution during 8-pole operation, the additional winding is arranged so that the total number of conductors per slot is greater in slots 2, 3, 6, 7, &c. than in slots 1, 4, 5, 8, &c. In a modification, the auxiliary coils are co-axial with the main coils, and this construction is stated to reduce the length of the coil heads. A starting winding may be provided, adapted to be changed over in the same manner as the main phase.