PURPOSE: To prevent serious trouble such as breaking pipe, by increasing the speed, permitting pump speed instruction at the time to return back for electric current, to which relates the previously determined speed-time, considering water hammer phenomenon, through which pressure increase will be in the allowable value.
CONSTITUTION: When the electric current is off, an arithmetic unit 2 and a speed setting signal change-over unit 3 operate by signal a from the detector 5, the signal from the speed setting signal change-over unit is met with the speed detecting signal c at point 7 as signal a through the arithmetic unit 2, running into Scherbius control unit 4 as deviation signal e to control the electric motor M. And then, constant speed increase ratio arithmetic unit is provided as an arithmetic unit 2, the first speed N0 is stored, speed N1 at the time to return back for electric current is outputted as speed set value, operating to increase the speed at constant increase ratio until the speed will return to the speed N0, sudden change in the water pipe is prevented by outputting the signal.
NAOI KOUICHI
TOMITA TSUYOSHI
