ESTIMATION TERMINAL PRESSURE CONSTANT CONTROL DEVICE FOR PUMP

摘要

PROBLEM TO BE SOLVED: To enable constant control of estimation terminal pressure in a pump water supplying device with high accuracy and a low cost. SOLUTION: Pressure sensors 2, 3 are connected to a water sucking supplying side discharge pipe passage 11 and a city water sucking side pipe passage 12 of a pump. A maximum set pressure is denoted by Pmax, while a minimum set pressure denoted by Pmin. Pressure differenceΔP is obtained by subtracting the suction pressure from pump discharge pressure per pumping flow amount. The pressure differenceΔP at the time of maximum flow amount Qmax is obtained from the relation between the thus obtained pressure differenceΔP and frequency characteristics of a variable speed device. The maximum frequency fmas at the time of the maximum set pressure Pmax is obtained from the relation between the frequency of the variable speed device and the pressure differenceΔP which is obtained by subtracting the intake pressure from the pump discharge pressure at the time of the minimum flow amount Qmin. The minimum frequency at the time of the minimum set pressure Pmin is denoted by fmin. Estimated terminal target pressure P is denoted by the following equation: P= Pmax-Pmin/(fmax-fmin)2}×(f-fmin)2--Pmin. The moving average of the target pressure P is obtained for comparing the target pressure P with a pump discharge pressure sensed value for controlling.