Electrical machines

Abstract

An electrical machine, such as an electric motor, dynamo or alternator has a casing with cooling vents enabling cooling fluid to flow into and out of the casing when the rotor of the electrical machine rotates. The rotor may be formed from conductive elements connected together at their outer regions by inter-connecting members which have vanes arranged to direct cooling fluid over the outer regions. Each conductive element is a metal strip with legs bent in opposite directions relative to the plane of the strip. Portions of the windings of the rotor are spaced apart to allow fluid to flow between the windings to enhance the cooling effect. With a current carrying rotor, varying the axial separation of the rotor and the stator varies the magnetic field intensity across the rotor.

1 . A conductive rotor for an electrical machine, having a current-carrying winding comprising a plurality of circumferentially distributed winding portions which lie in at least one winding plane perpendicular to the rotor axis, and extend from a radially inner region to a radially outer region, and a commutator provided by surfaces of the winding portions, the winding being formed of a plurality of integrally formed conductive elements each comprising a metal strip, in which the surfaces providing the commutator are edge surfaces of the metal strip, said edge surfaces being spaced apart from each other to allow fluid flow therebetween for cooling the commutator.  
     
     
         2 . A conductive rotor as claimed in  claim 1 , in which the major surfaces of the metal strip are coated adjacent the commutator with an insulating material.  
     
     
         3 . A conductive rotor as claimed in  claim 2 , wherein said insulating material has a relatively low wear resistance so that it will readily wear or break away from said major surfaces at their portions adjoining said edge surfaces as the commutator wears during use.  
     
     
         4 . A conductive rotor as claimed in  claim 3 , wherein said insulating material is a coating formed by baking a powder coating applied to said conductive sections.