1外文文献原稿和译文外文文献原稿和译文原原 稿稿The water supply system is the national production and life indispensable important one annulus. The traditional method of water supply area, water pollution, infrastructure investment, but the main drawback is that water can not be kept constant, causing part of the equipment can not work normally. Variable frequency speed control technology is a new mature AC motor stepless speed regulating technology, its unique excellent control performance is widely applied to the speed control field, especially in water supply industry. Due to the safety in production and the water quality of special needs, for constant pressure water supply with the stringent requirements, so the frequency control technology has been more in-depth application. Constant pressure water supply ways to advanced technology, constant pressure, convenient operation, reliable operation, energy saving, high degree of automation, in pump station water supply can perform the following functions:( 1) to maintain constant pressure;( 2) the control system can be manual or automatic operation;( 3) a plurality of pump automatic switch operation;( 4) system of sleep and wake, when people stop when water, the system is in a sleep state, until the water demand automatically wake;( 5) adjusts the PID parameters on line;( 6) pump unit and circuit protection detection alarm, signal display.The actual pressure of the pipe network feedback and a given pressure were compared, when the pressure of a pipe network is low, increase the output of frequency converter, pump speed faster, water supply quantity increases, forcing the pipe network pressure rise. Vice pump speed slow down, reduce the water supply pipe network pressure drop, to keep the constant pressure water supply.System hardware structureSystem uses a pressure sensor, PLC and inverter as a central control device, to achieve a desired function. Source: network transmission and distribution equipment 2installation in pipe line pressure sensor, for detecting the water pressure of the pipe network, converting pressure is 4 20 mA current or voltage signal is 0 10V, supplied to the inverter.Converter pump motor control device, in accordance with the constant water pressure needs to be 0 50 Hz frequency signal supply pump motor, adjust its speed SAJ converter is powerful, i.e. pre-programmed set parameter set, will use the required in the process of setting the number of parameters is reduced to a minimum, default value according to the application parameter of the macro choice and different. The system adopts the PID control application macro, closed loop control. Inverter based on a constant pressure corresponding to the voltage setting value and from the pressure sensor to obtain the feedback current signal, the use of PID control macro automatically adjust, change the frequency output value to adjust the control the speed of the pump motor, to ensure that the pipe network pressure constant requirements.The application of inverter in the constant pressure water supply一The characteristic and analysis of variable frequency speed regulationThe water users in general is dynamic, so the water supply is insufficient or excess water supply situation has occurred. The water supply and the imbalance between the concentrated reflection in water supply pressure, namely water and water supply is less, the low pressure; less water consumption and water supply, the pressure. Keep the water pressure constant, can make the water supply and water balance between water supply and water for a long time, that is, less water when the water is less, so as to improve the quality of water supply.Constant pressure water supply system for the user is very important. In production and living water, if water supply due to insufficient pressure or short of water, may affect the quality of life, serious when can influence the survival safety, such as when a fire occurs, if the water pressure is insufficient or water supply, can quickly fire, may cause significant economic losses and casualties. Therefore, water area by means of Arts is the constant pressure water supply system, can produce great economic benefit and social benefit.With the development of electric power technology, frequency conversion technology perfected, with variable frequency speed control as the core of the 3intelligent water control system replaced the previous high level water tank and a pressure tank and water supply equipment, stable starting, the starting current can be limited within specified current, thereby avoiding the starting time of the impact of power grid; because the average rotational speed of pump is reduced, which can extend the pumps and valves and other things of life; to eliminate the start and stop of the water hammer effect. The stable and safe performance, simple and convenient operation, and complete and thoughtful function, will make the water supply and water conservation, energy saving, labor saving,