Apparatus for providing an electrical generator with a constant rotational speed from a variable speed input

An electrical generator drive having a power source which is able to transmit power at a rotational speed subject to progressive and stepwise speed changes, an electrical generator which requires a rotational input of power at a substantially constant speed, and a controllable drive transmission of high rotational inertia coupling together the power source and the electrical generator, said drive transmission comprising:

• an epicyclic gear having an input member which is arranged to be driven by said power source, an output member coupled with said electrical generator, and a reaction member;
• monitoring means arranged to respond to fluctuations from a predetermined value in the rotational speed of the output member;
• and control means including a hydraulic pump/motor unit coupled with said reaction member and controllable by the monitoring means in order to vary the relative rotation between the reaction member and the other members of the epicyclic gear so as to maintain a substantially constant predetermined speed of the output member;
• in which:
• the monitoring means includes an electrical control unit having a memory storable with a predetermined value corresponding to the predetermined speed of the output member, means for feeding to the control unit an input signal which represents the actual speed of the output member and which the control unit compares with the predetermined speed of the output member, and an electrical control line from the control unit to said pump/motor unit via which the control unit controls the operation of the pump motor unit to cause alteration in the relative rotation of the reaction member, when a fluctuation occurs in the speed of the output member, and such as to restore the speed of the output member to the predetermined speed;
• and the drive transmission also includes at least one flexible coupling for torsionally absorbing at least part of any speed fluctuations imparted to the drive transmission via the power source and the input member.