Design Of Variable Frequency Constant Pressure Water-supply System Controlled By PLC

Along with the high speed development of Chinese economy, industrial enterprise production scale expands unceasingly, Industrial enterprise on production process control precision improves constantly, and enterprise water supply system is developing very quickly. At the same time, soft and hardware infrastructure construction of water supply system also need higher request. And this system is an important part of industrial enterprise’s reliability and stability. Water supply system affects industrial enterprise production safety continuity. Because low efficiency and automation level, the traditional methods of industrial enterprise like the pump pressurization water supply and the jar etc.are difficult to satisfy the needs of current industrial production.Based on the requirement of water supply in a industrial enterprise of Dalian, an system by using variable frequency and controlling, which is composed of low voltage electrical equipment transducer,PLC, pumps, motors is designed to. This system has functions of automatic work frequency operation, automatic constant pressure operation and the function of long-range control by hand. This system has solved efficiently problem.First of all, according to the output power of the motor and pump speed is proportional to the three times, this paper analyses the energy saving principle of this system.The control model and the approximate mathematical model are also established. The frequency converter with built-in PID module to realize the closed loop speed control system. The water flow with frequency pump mutual investment security supply and variable frequency pump grading adjusting water supply mode can not only ensure the lowest safe water flow and also high flow constant pressure water supply and energy saving.Secondly, this paper discusses the two motor mutual investment reserves for minimum security of water supply idea and implementation method, discusses a variety of effective supply states and the switching conditions of four pumps parallel water supply mode. This paper also discusses the PLC control software program flow, electrical control scheme, PLC software, PID parameter setting, motor relay protection setting and some other issues in depth.At last, through the research of computer and PLC communication connection, this paper discusses the computer communication network, remote monitoring and fault alarm function.