Abstract: An electrical machine apparatus for starting an internal combustion engine and supplying voltage to an on-board electrical system of a motor vehicle having a main gear, includes an electrical machine, a planetary gear through which the electrical machine is coupleable to the engine, the electrical machine being switchable over from a motor mode to a generator mode, the gear being switchable over for adjusting an rpm of the electrical machine, the electrical machine being coupleable to a drive train of the engine via the gear so that for synchronizing the main gear, speed-changing stages in the gear and thus a moment of mass inertia of the electric machine are selectable in accordance with a desired rpm adaptation of the drive train.