Abstract: A compressor system for a turbo machine is provided. The turbo machine includes a low-pressure shaft coupled to a low-pressure turbine and a high-pressure shaft coupled to a high-pressure turbine. The high-pressure shaft and the low-pressure shaft are rotatable about a central rotational axis. The compressor system includes a fan driven by the low-pressure turbine via the low-pressure shaft, a booster compressor and a gear unit. The low-pressure shaft is coupled to a first input member of the gear unit. The high-pressure shaft is coupled to a second input member of the gear unit. An intermediate rotor is coupled to an output member of the gear unit. The intermediate rotor includes rotatable elements of the booster compressor and an electric motor-generator. The intermediate rotor is driven by the low-pressure shaft and the high-pressure shaft.

Abstract: In a gas turbine engine, the booster compressor is driven by both the low pressure or fan shaft and high pressure shaft through a differential gear arrangement. The rotational speed of the booster compressor is intermediate between the speed of the fan and the speed of the high pressure compressor.