Patent ID: 7788898

Claim:
A system for variable coupling of a high pressure spool and a low pressure spools to power a generator in a turbofan engine, the system comprising: a differential gear portion having a first input portion, a second input portion, and an output shaft; an electromagnetic variable transmission having an independently rotatable inner rotor portion and an independently rotatable outer rotor portion, the inner rotor portion coupled with one of the high pressure spool and the low pressure spool, and the outer portion connected to the other spool, to transfer torque between the high pressure spool and the low pressure spool; the differential gear portion being connected between the high pressure spool and the low pressure spool in parallel with the electromagnetically variable transmission; the generator mechanically coupled to the output shaft; wherein the differential gear portion being arranged to equalize a rotational speed of the high pressure spool, a rotational speed of the low pressure spool, and an output speed of the output shaft for driving the generator; and the EVT arranged to controllably couple power from the low pressure spool to the high pressure spool.