Multi-rotor A.C. electric drive device

Claim 1

An A.C. electric device used for driving a machine, including an electromagnetic portion; said electromagnetic portion including a stator and at least a main rotor and an auxiliary rotor; said stator having a core for conducting magnetic flux, and a winding capable of generating a rotating or an alternating magnetic field when a suitable A.C. power is supplied; said main and auxiliary rotors also having their own respective cores for conducting magnetic flux, and both said rotors being capable of producing torques at asynchronous speed under the effect of a rotating or an alternating magnetic field; wherein said main rotor has a closed winding or a conductor equivalent to the closed winding for conducting induced current; said electromagnetic portion has a first closed magnetic circuit and a second closed magnetic circuit both linked with said winding or said conductor of the main rotor; the first magnetic circuit links with said winding of the stator, and includes the core of the stator and a part of the core of the main rotor, but not the core of the auxiliary rotor; the second magnetic circuit includes the other part of the core of the main rotor and at least a part of the core of the auxiliary rotor, but not the core of the stator; whereby, the current in the winding of the stator can excite in the first magnetic circuit a main flux capable of driving the main rotor to rotate and thereby induce a current in the winding or conductor of said main rotor; said induced current in the winding or conductor of the main rotor can excite in the second magnetic circuit a main flux capable of driving the auxiliary rotor to rotate; and said main flux excited by the current of said stator winding in said first magnetic circuit does not pass through the core of the auxiliary rotor.