| 摘要 |
PURPOSE: To suppress pressure fluctuation to possible minimum and perform optimum pressure control of a water distribution pump by determining the number of pumps to be speed controlled in compliance with the size of the absolute value of the difference between the discharge pressure measured value and the set value. CONSTITUTION: A discharge valve 3 and a discharge pressure gauge 4 are installed on the discharge side of a water distribution pump 2 which distributes water to users 20 from a clear water basin 1. A pressure control device 6 of this pump 2 has a subtracter 7 which calculates the deviation of the actual measurement from the target value for the pump 2 discharge pressure. The absolute value of the obtained deviation is computed by an absolute value calculator 8; if the resultant value is greater than the valueα1 set previously in a number-of-units setting device 9, three units are put under speed control, and if is smaller thanα1 and greater than the separately set valueα2, two units are put under control, and in the case smaller than the valueα2, one unit is put under control. In accordance with the predetermined priority, the unit(s) to be speed controlled are decided by a unit No. deciding device 10 among the pumps in operation currently so that the number of units as specified by computation with the device 9 is attained, and speed control of the applicable unit is performed upon the calculation given by a PID controller 5.
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