GB1243657A - Improvements in and relating to rotating field motors for single-phase operation - Google Patents

Abstract

1,243,657. Electric motors; control of A.C. motors. THRICE-TITAN A.S. 11 Nov., 1968 [10 Nov., 1967], No. 53309/68. Headings H2A and H2J. A simple phase rotating field motor comprises at least two pairs of stator windings. e.g. 1, and 2, 2<SP>1</SP>, Fig. 1, each winding having a series connected controllable conductor element, e.g. 4, 4<SP>1</SP>, such as a thyristor, transistor or thyratron, all of the series connected windings and conductor elements being parallel connected to the supply, and in use the conductor elements are each controlled to conduct for a period equal to or less than a half period of the A.C. supply so as to produce an approximately rotating field. By varying the turn-on time of the conductor elements rotating fields of a variety of speeds may be obtained, the field being either continuous, Fig. 2, or intermittent, Figs. 3, 6 (both not shown). To form a better rotating field the turn-on times of conductor elements in adjacent winding pairs, e.g. 4, 5, may overlap, as shown or, for a fixed speed motor, the m.m.f.'s produced by the different windings may be equalized, either by forming more turns on those windings which conduct at points on the voltage cycle remote from the peak, or by forming those windings which conduct at the peak of thinner wire than the other windings. Each winding, in any of the above embodiments, may be divided into two parts, the controllable conductor element being connected between the two parts.