GB379383A - Improvements in and relating to synchronous electric motors - Google Patents

Abstract

379,383. Motors. FERRANTI, Ltd. and HOLMES, W., Hollinwood, Lancashire. May 1, 1931, No. 12942. [Class 35.] Motors with unwound iron armatures.-A synchronous motor comprises a bi-polar constant field system, e.g. a permanent magnet a having two north polepieces b and two south polepieces b<1>, and a rotor consisting of a pair of rigidly connected discs c, d of magnetizable material alternately polarized to opposite polarity, each associated with a pair of polepieces of opposite polarity, the arrangement being such that when there is minimum reluctance between one disc and, say, the north polepiece associated therewith and maximum reluctance between it and the south polepiece, the reverse conditions exist for the second disc. The rotor discs are polarized by an electromagnet k excited with alternating current and having polepieces g, h extending in proximity to the discs. The motor is started by imparting an impetus to the:rotor and to facilitate synchronizing, a flywheel o may be coupled to the non- magnetic rotor sleeve e by a spring p. After synchronism has been reached the flywheel may be thrown out of operation manually or automatically. In a modification, the permanent magnet polepieces co-operate with internal projections on annular rotor discs.