Slotless armature DC machines with multiplex connection

The slotless armature has been shown to give greatly improved commutation in DC machines. The use of multiplex windings allows the designer to take advantage of the improved commutation to increase the maximum power/diameter ratio from about 2 MW/m to about 6 MW/m. With a conventional slotted armature, multiplex connection can lead to problems of irregular distribution of voltage around the commutator and of current between the various parallel paths, but, in a slotless armature, the turns may be uniformly distributed over the core and these problems do not arise. Machines of much higher power become possible with armatures of manageable size and weight, and more economical designs become available for machines of modest power. A set of tests using a full size DC traction motor fitted with experimental slotless multiplex windings confirms the findings