GB332174A - Improvements in synchronous electromotors - Google Patents

Abstract

332,174. Kienzle Uhrenfabriken Akt.- Ges. Dec. 8, 1928, [Convention date]. Motors with unwound iron armatures; alternating-current motors; cores. - In a synchronous motor for driving clocks and the like a field magnet is employed which has on each side of a plane of symmetry through its centre only poles of one sign, these being in the normal positions which poles of that sign occupy in a series wherein poles of opposite sign alternate in the usual way. Fig. 2 shows the disposition for a 10-pole field wherein three poles of common sign are retained on each side of the plane of symmetry A-B. Two poles on each side, denoted by (N) (S) are omitted. Fig. 3 shows the iron construction for a 6-pole machine with a 6-tooth rotor. On the two sides of the plane A-B the central poles are omitted, leaving a pair of north poles c, d and a pair of south poles e, f. The core is divided on the line A-B, so that one type only of half-laminae is required. To make the motor self-starting, the poles are split and provided with " screening " coils h, thus giving a rotary starting field. Shoulders i, k are provided for making the leakage field of the magnet more effective in actuating an auxiliary armature m for giving a signal or starting an ordinary clock in the event of failure of the current.