Abstract This invention relates to a rotor assembly for use in a dynamo electric machine, the rotor assembly having two parts which are mounted on a rotor shaft, each of the paths having a periphery a plurality of pole pieces of generally trapezoidal shape which extend in a direction substantially parallel to the axis of the rotor shaft. The pole pieces of the two paths are interdigitated and arranged such that in use the pole pieces associated with the two parts have opposite polarities, the non parallel sides of each pole piece being spaced from the adjacent sides of adjacent pole pieces and a portion of the outer face of each pole piece being of part cylindrical configuration. The outer edges of the sides of each pole piece when seen in developed plan view are inclined relative to the rotor axis by different amounts and a relieved portion is provided in the outer face adjacent to one of these edges so that the part cylindrical portion of the outer face has substantially the shape of an isoscelese trapezium.
In a rotor assembly for use in a dynamo electric machine, said rotor assembly including a rotor shaft, two parts which are mounted on the rotor shaft and a plurality of pole pieces at the periphery of each of said parts, said pole pieces being of generally trapezoidal shape which extend in a direction substantially parallel to the axis of the rotor shaft, the pole pieces of the two parts being inter-digitated and arranged such that, in use, the pole pieces associated with the two parts have opposite polarities, the non-parallel sides of each pole piece being spaced from the adjacent sides of adjacent pole pieces and a portion of the outer face of each pole piece being of part cylindrical configuration, the improvements comprised by: a. the outer edges of each pole piece when seen in developed plan view being inclined relative to the rotor axis by different amounts, b. an abrupt relieved portion being provided in said outer face adjacent to one of these edges to define a further edge between the relieved portion and said part cylindrical portion so that said part cylindrical portion of the outer face has substantially the shape of an isosceles trapezium, and c. the outer edge of each pole piece having an undercut relief whose inclination relative to the outer face of that pole piece varies along the length of the latter so that the flux leakage distance between said edge and the adjacent edge of the adjacent pole piece remains substantially constant over the length of the pole piece.
Claim 2
Dependent Claim
258 words
In a rotor assembly for use in a dynamo electric machine, said rotor assembly including a rotor shaft, two parts which are mounted on the rotor shaft and a plurality of pole pieces at the periphery of each of said parts, said pole pieces being of generally trapezoidal shape which extend in a direction substantially parallel to the axis of the rotor shaft, the pole pieces of the two parts being inter-digitated and arranged such that, in use, the pole pieces associated with the two parts have opposite polarities, the non-parallel sides of each pole piece being spaced from the adjacent sides of adjacent pole pieces and a portion of the outer face of each pole piece being of part cylindrical configuration, the improvements comprised by: a. the outer edges of each pole piece when seen in developed plan view being inclined relative to the rotor axis by different amounts, b. an abrupt relieved portion being provided in said outer face adjacent to one of these edges to define a further edge between the relieved portion and said part cylindrical portion so that said part cylindrical portion of the outer face has substantially the shape of an isosceles trapezium, and c. the outer edge of each pole piece having an undercut relief whose inclination relative to the outer face of that pole piece varies along the length of the latter so that the flux leakage distance between said edge and the adjacent edge of the adjacent pole piece remains substantially constant over the length of the pole piece.