Abstract: A nuclear rector feed-water system in which water is fed to a reactor pressure vessel by a reactor feed-water pump, including a current command value operating unit for comparing a reactor water level setting signal setting a reactor water-level in a reactor pressure vessel with either one of a signal obtained by adding or subtracting a reactor water level detection value, a main steam amount flow rate detection value of a flow rate of the main steam introduced into a steam turbine from the reactor pressure vessel, and a reactor feed-water flow rate detection value of an amount of feed-water fed to the reactor pressure vessel, or reactor water-level detection value, and operating and then outputting a current command value based on comparison result a revolution/torque operating unit for operating revolution number command value and toque command value of the reactor feed-water pump in response to the current command value inputted in the revolution/torque operating unit and a semiconductor power conversion c

Abstract: In a reactor feed-water system in which water is fed to a reactor pressure vessel by at least one reactor feed-water pump, a driving power for a feed-water pump drive motor is supplied from a semiconductor power conversion circuit adopting a self-excitation switching device; a reactor water-level detection value, a main steam flow rate detection value and a rector feed-water flow rate detection value are calculated by adding or subtracting these values; and a comparison result between the result of the calculation and a reactor water-level setting signal is given, as current command value to an inverter, to the inverter of the semiconductor power conversion circuit, thereby controlling the revolution number and torque of the feed-water pump drive motor, thus controlling the reactor feed-water flow rate.