GB1396305A - Ac synchronous motors - Google Patents

Abstract

1396305 A.C. synchronous motors SANGAMO WESTON Ltd 8 May 1972 [6 May 1971] 13430/71 Heading H2A In an A.C. synchronous motor comprising a permanently magnetized rotor 28 having peripheral poles of alternate polarity, a stator comprises two main stator parts, e.g. a plate 10 and a cup 12 enclosing an excitation coil 29 and respectively having a plurality of main poles 12 extending in opposite axial directions, two auxiliary cup-shaped stator parts 14a, 14b respectively, axially inwardly of the main parts and respectively having a plurality of auxiliary poles 16 extending in opposite axial directions and which produce fluxes phase-shifted from those produced by the main poles 12 the auxiliary stator parts being discrete from the main stator parts and all the main poles and all the auxiliary poles being grouped together in respective opposite arcs of the same radius, and a short-circuiting shading ring 18a, 18b positioned between each pair of associated main and auxiliary stator parts, the outer diameter of each ring being less than the diameter of the circle on which the poles lie each ring being located radially inwardly of the main poles and the associated auxiliary stator part being seated on the shading ring axially inwardly thereof. The two sets of main poles 12 and of auxiliary poles 16 are respectively interdigitated and, as Fig. 3 shows, the respective arcs extend over less than, and more than, 180 degrees. Disposed within each shading ring, e.g. of Cu, is an iron spacer ring 20a, 20b. The rotor, a ferrite annulus is mounted via a moulded plastics bush on a plain steel spindle 26 carried in a single bearing bush 24, and noise is suppressed by a leaf spring 27 which preloads the spindle against an end thrust plate 25. By pre-setting the displacement angle 180-# of the main and auxiliary poles 12, 16 about its line of symmetry the direction of rotation may be selected, or a modification states that this may be achieved by so coupling the two stator parts together as to permit relative angular movement by an external control.