An auxiliary armature squirrel cage and a secondary commutating field in DC machines

A proposal is put forward for a system which would produce effects similar to an interpole in DC machines and which could prove a better alternative for this purpose than the banding on the armature end windings. The system consists of a squirrel cage which occupies the same slots with part of the armature winding. For the same nominal length of cage as the banding, the cage will have the greater effect; this is because of the higher intensity of its `commutating¿ field and of its greater reactance to resistance ratio. The section of the armature which incorporates the cage will be prefabricated and then mounted on the shaft before the armature windings aie inserted; the assembly of the armature therefore would not present any additional problems when compared to a conventional machine.