Abstract: A power generator system that is suitable for use on medium-sized and large watercraft. The system includes a generator that is driven by a hydraulic motor that is coupled to the main engine through a variable hydraulic pump. In order to maintain a stable, substantially constant-frequency power output from the generator as the main engine operates over a wide range of operating speeds, a controller receives a power frequency input signal and a hydraulic pump speed input signal, and uses both of these input signals to generate an output control signal to the hydraulic pump to maintain a substantially constant fluid flow to the hydraulic motor. The frequency signal is used to determine whether to increase or decrease the fluid flow, and the pump speed signal is used to determine the rate of change of the fluid flow in order to avoid overshooting the desired frequency.

Abstract: A system for operation of an electric generator from a main engine having a varying rotational speed comprises a variable hydraulic pump connected to and driven from the main engine, a hydraulic motor arranged to be driven by the hydraulic pump and to drive the electric generator, and a means for regulating the oil quantity from the pump in dependence on electric control signals supplied from an electronic frequency controller. The frequency controller is connected between a voltage output of the generator and the regulating means and is arranged to deliver said control signals in dependence on frequency deviations on the generator output, to thereby maintain the oil quantity from the pump, and therewith the generator frequency, constant.