外文翻译--恒压供水.doc

Constant pressure water-supply With the progress development of social economic and the construct scale of city continuously enlarge, increasing of population and standard of living of people continuously improved, more and more demanding to quantity, quality and stability of water supply bring forward in city. The automatic degree of waterworks in town is much lower than the correspondence in city. Especially in some old waterworks, the equipment of automatic control system is dropped behind. The control of unit ismainly depended on manual operating of watches. The process of control is very complicated and that manual control cant meet the change of pressure in the pipes and the water level of the pure pond. It also cant act the proper feedback in time. For the sake of water supply, the electromotor unit usually works in the state of over charge. Not only efficiency of electromotor is low and electricity consuming is bigger, but also the pressure of pipes is overload in long term. On the basis of analyzing status in quo of the waterworks in our country, this paper designs a suit of constant pressure water supply automatic control system by using variable frequency speed-regulating technology based on PLC. The system is made up of PLC, transducer, units of pumps and electromotors, pressure sensor, industrial control computer and console. The system is used a transducer to make four electromotors starting, running and timing. The two high-power electromotors(220Kw) and low-power electromotors(160Kw) is partly circulated. To connect control computer with PLC and realize supervisal, a real time supervisal control software of water supply system is developed. The software has the function of data connection, communication, state control of facilities and data management. To tune up the frequency of power supply by the transducer in the system, this adjusting make the speed of electromotor and performance curve of pump change. At last, it make the