GB944438A - Improvements in or relating to dynamo-electric machines - Google Patents

Abstract

944,438. Dynamo-electric machines. F. FAULHABER. April 14, 1961 [April 14, 1960], No. 13526/61. Addition to 903,285. Drawings to Specification. Heading H2A. In a dynamo-electric machine as described in the parent Specification, the commutator is provided with an odd number of collector segments, the radial magnetic field traversing the cylindrical winding occupying the annular air gap between the fixed permanent magnet and the surrounding iron yoke is designed to have a value which varies sinusoidally in a circumferential direction and the commutator brushes are so positioned with respect to the stationary magnetic field that the integrated sum of the torques applied to the cylindrical winding (a) when no commutator segments are short-circuited one to another, and (b) when two commutator segments are so short-circuited, weighted to take account of the times for which they are respectively effective, are maximized. By using an odd number of commutator segments the frequency at which the variation in torque, due to periodic shortcircuiting of adjacent segments together, is increased over that obtained when a similar even number of segments is used, while the amplitude of the variation is reduced. By suitably positioning the commutator brushes with respect to the stationary magnetic field, the overall torque, derived by compounding the products of the magnetic induction and current distribution in the coils for both possible condition of the commutator, may be arranged to achieve a maximum value.