Asynchronous intergrid transfer apparatus

Apparatus transferring electric power between two polyphase electric circuits, the apparatus comprising a rotating machine and a torque motor, the rotating machine comprising

• a first set of windings having a predetermined number of poles, the first set of windings electrically connected to a first of the circuits and generating a first rotating magnetic field having a predetermined direction of rotation about an axis, and
• a second set of windings having the predetermined number of poles, the second set of windings electrically connected to the second circuit and generating a second rotating magnetic field having the predetermined direction of rotation;
• and connection means operatively connecting the torque motor intermediate the two sets of windings so as to apply a torque therebetween, the magnitude of the applied torque controlling the magnitude of the power transferred.

A method of transferring electric power between two polyphase electric grids, the method comprising the steps of:

• a) connecting a first of the two grids to a first set of polyphase windings having a first predetermined number of poles, thereby producing a first rotating magnetic field having a first predetermined direction of rotation about an axis,
• b) connecting the second grid to a second set of polyphase windings rotatable with respect to the first set of windings, the second set of windings having the predetermined number of poles, thereby producing a second rotating magnetic field coincident with the first magnetic field and rotating in the predetermined direction,
• c) applying a torque between the two sets of windings, the torque applied to the first set of windings in the predetermined rotational direction to transfer power from the second grid to the first grid, the torque applied in the opposite rotational direction to transfer power from the first grid to the second grid.