designandimplementationofavariablefrequencyregulatorysystemforwatersupply-外文文献(编辑修改稿)

designandimplementationofavariablefrequencyregulatorysystemforwatersupply-外文文献(编辑修改稿)内容摘要：

k Diagram of a Variable Frequency Constant Pressure System for Single Pump Water Supply System. In this system, both flowrate and the resistance of pipes are varying because the flowrate is proportional to number of valves to be opened. Curve 3 represents the resistance of pipe when the flowrate reaches the maximum point. It intercepts with the H* Q* at point a which is the set point for operation. Curve 4 is for resistance of pipe when the flowrate is less and only part of valves to be opened. If there is no frequency regulator, it works at point b39。 only. At this moment, the head pressure exceeds the set value. The flowrate Q is proportional to the speed of the pump, n. Head pressure H is thus proportional to the square of the speed, n2. The speed of the pump can be controlled by the frequency regulator. It bees the curve 2, which intercepts curve 4 at point b, it is a new set (working) point. At this time, the set speed should be n* = n/nN = K (Kl). Obviously, the point b is lower than point b39。 . It in turn means that H at point b is less than that at point b39。 . Hi, Hw It achieves the purpose of energy saving. 4 3 i39。 n*=l I / 1 .o 1 I I I I k I * Q* Fig. 2 : Static Characterisitcs of the Water Supply System. FURTHER MODIFICATION This JSSP1 model was suitable for single pump water supply system. When the flowrate is little, the pressure can be much reduced. For example, Hp* varies from 1 to Hp* which is less than 1 (Hps* 1). It is able to save much energy. From this working principle, it was modified to suit a large scale multiple pumping water supply system. A new model of JS5P2 was then developed. Fig. 3 shows a block diagram of a variable frequency constant pressure system consisting of 3 same capacity pumps. It was modified from the JSSP1 model. It is designed for multi .pumps water supply system which programmable logic control (PLC) is involved such that the number of hydraulic motors in operation can be determined by the flowrate. The rest of motors are in standby mode and the energy saving can be realized. From Fig. 3, the system was po。