| 摘要 |
PURPOSE:To smoothly control the discharge flow rate of a pump, by a method wherein a water level in a discharge tank is estimated from a flow-out quantity from the discharge tank, an actual head is found from the water level and a water level in a pump well, and a pump resistance curved line is found to operate a pump at the number of revolutions of the pump corresponding to a set flow rate. CONSTITUTION:The flow-out quantity of a discharge tank 3, actually measured by a flow meter 4, is substituted for a formula (1) to find a water level in the discharge tank 3 by means of a computer 12. In the formula, A is a cross section area, K is a coefficient, (g) is the acceleration of gravity, and H is a difference in water level. From a water level found by the computer 12 and a water level in a pump well 1 measured by a level gauge 5, the actual head of a pump 2 is found by a comparator 11. In a function generator 10, pump characteristics, indicated by means of a discharge quantity Q and a head H, are stored, the resistance curved line of a pump is decided from an actual head previously found, and the number of revolutions of a pump, corresponding to a set flow rate 6, is decided by the actual head curve. This operates the pump 2.
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