JP2874408B

PURPOSE:To remove a fault that, in a Pelton wheel with plural number of nozzles whose operating number is automatically changed over to highly effective operating number according to the output of a hydraulic turbine, the total opening of a needle valve is overshot or undershot by the regulating error of a needle valve positioning switch or the unevenness of the end time of changing over to cause fluctuation in the output of the hydraulic turbine. CONSTITUTION:During changing over process executed by a nozzle changing over command, a signal 21 for nozzle being in changing over process is sent out to turn off the contact 13b of an opening command value changing section and to turn on the contact 13a, and the opening command value sent from the contact 13a is given to an opening adjusting section 6 to control a nozzle opening instead of an opening command value 12 on the side of a governor. On the other hand, a target opening computing section 14 computes the target opening after changing over the nozzles on a needle opening command value 22 at the time of receiving a changing over command, nozzle increasing and decreasing commands 23, 24, and the present number of operating nozzles. An automatic follow-up circuit 16c receives the computed target opening to send out the opening command value following from present opening toward the target opening to the contact 13a.