GEAR SYSTEMS WITH VARIABLE SPEED DRIVE

An epicyclic gear system (100) includes an input sun gear (102) configured to receive rotational input from a turbine (104) of a turbo charger. A first set of planet gears (106) is distributed around and meshes with the input sun gear (102). A carrier (108) holds the first set of planet gears (106) and defines a rotational axis (A) about which the carrier (108) rotates. A second set of planet gears (110) is mounted to the carrier (108). An output sun gear (112) is included, wherein the second set of planet gears (110) are distributed around and mesh with the output sun gear (112). The output sun gear (112) is configured to deliver rotational power to an internal combustion engine (114). The carrier (108) is configured to selectively be driven by a variable speed drive (116) to regulate output to the output sun gear (112) over a range of input rotational speeds of the input sun gear (102).