Abstract: Electric induction motors are either of the cylindrical or axial air-gap types; disadvantages of the former type, which is the more common in use, are in part overcome by the latter type, but the invention provides a new concept in electric induction motors and drive assemblies of the axial air-gap type, which eliminates the need for maintenance and substantially removes the need for skilled personnel for inspection, cleaning, modification or even installation. Induction drives according to the invention have a virtually instantaneously replaceable stator core, so that a failed stator winding can be overcome by removing it and fitting a new one, so that continued use of the electric drive can be resumed after a few minutes downtime only. Various structural arrangements for achieving this are disclosed.

Abstract: An electrical synchronous machine, i.e. an alternator or synchronous motor, comprises a rotor having field coils of alternating polarities arranged on core elements of magnetic material and spaced around its axis so as to produce a magnetic field extending away from the core elements and towards a stator which has windings disposed on an annular magnetic core, the rotor and stator being arranged substantially coaxially with the rotor core elements confronting the stator core. The machine can be installed quickly in a variety of ways by unskilled personnel and the field coils and stator core can be replaced without dismantling or disturbing the machine. Permanent magnets disposed in the field coil core elements augment excitation during starting. Auxiliary windings associated with the field coil core elements regulate speed and enable the machine, when acting as a motor, to be self-starting. The latter function is assisted by connecting all of the field coils in a closed loop.