the charge pump casing 9 for instance in operation of hydrostatic pump 1 charge pump 12 is driven via a hollow input shaft 11 connected to the planet wheel gear carrier 22 the sun wheel 21 driving the planet wheel 22 carrier is connected to the drive shaft 3 of hydrostatic pump 1 such that charge pump 12 provides a charge pump flow rate according to the rotational speed of hydrostatic pump 1 if at the same time ring gear 23 is standing still the rotational speed of ring gear 23 and therewith the rotational speed of charge pump 12 can be adapted to the necessary charge flow rate for the closed hydrostatic circuit not shown by controlling the rotational speed of charge pump motor 30 fig2 shows another embodiment of the inventive charge pump system 10 in which the ring gear 23 is driven by a worm gear 16 arranged on the outer side of ring gear 23 thereby the worm gear 16 is driven by a charge pump motor 30 however in fig2 the charge pump motor 30 is shown connected in parallel via a driving shaft 31 to worm gear 16 this is for illustration reasons only as the charge pump motor 30 is arranged preferably in direction of.