Patent ID: 8054011

Claim:
A variable frequency transformer comprising: a plurality of rotary transformers each including a rotor winding, a stator winding and a drive motor; a first parallel circuit including at least two of the rotary transformers arranged in parallel and having an isolating circuit breaker connected to a first winding of each of the at least two of the rotary transformers in the first parallel circuit, wherein the first winding is the rotor winding or the stator winding, and a separate synchronizing circuit breaker connected to each of a second winding for each of the rotary transformers in the first parallel circuit, wherein the second winding is the rotor winding or the stator winding which is not the first winding; a first main transformer having a first winding connectable to a first power grid and at least one secondary winding connectable to the isolating circuit breaker in the first parallel circuit; a second main transformer having a first winding connectable to a second power grid and at least one secondary winding connectable to each of the synchronizing circuit breakers in the first parallel circuit, and a control system operatively connected to each of the synchronizing circuit breakers, the isolating circuit breakers and the drive motors for each of the rotary transformers.