The Design Of Variable Frequency Constant Pressure Water Supply System Based On PLC

Along with the development of the socio-economy of our country,the housing system is going deep into reforms,and people's living standard is being improved.At the same time,in the city,each kind of sub-district construction is developing very quickly, which puts forward higher requirement for the infrastructure construction of sub-district. And the construction of sub-district water supply system is an important aspect in which. The reliability,stability and economy of water supply directly affects sub-district household's normal life and work,and also embodies the difference in the level of sub-district property management.The traditional means of water supply such as the pump pressurization water supply at constant speed,water tower of upper cistern,the jar etc.are hard to satisfy the needs of current economic life,because low efficiency,reliability and automation level are all commonly existing in these means.According to the requirement of water supply in a abiding place of Lan Zhou,a set of automatic system of constant pressure water supply by using variable frequency and remote monitoring and controlling,which is composed of PLC,transducer,pressure sensor,pumps and electro-motors,computer and device of communication is designed to that end.This set of system has the functions like automatic constant pressure operation by using variable frequency,automatic work frequency operation,and the function of long-range control by hand and the on-the-spot control by hand etc.The system has solved efficiently the problem existing in the traditional way of water supply,which has various supplementary functions to strengthen the reliability.The system has an organic combination with computer and promotes the systematic overall performance.Based on that the three side of the pump water delivery rate and the pump rotational speed become direct ratio,the paper analyses the mechanism of energy saving that the way of water supply by using the method of variable velocity variable frequency is superior to the traditional way of constant pressure water supply controlled by valve. Setting up in advance the parameter of the PH)modular built-in the transducer,a system of closed circuit using the feedback of hydraulic pressure of far biography pressure table has formed.According to the change of water consumption,with PID,in the sphere of whole rate of flow,combining the constant regulation of the pump of frequency conversion with the work frequency pump grade regulation,the system of closed circuit can realize the constant pressure water supply and save energy efficiently.This paper discusses the reasonability of water supply scheme with much pump parallel connection,and analyses the conversion condition and the various states of water supply of the much pump way of water supply as well as the switch process and the problem of a generator from variable frequency operation mode to work frequency operation mode.This paper has also given the electrical design scheme and PLC controlling program scheme that realizes effective state circulating conversion control.By researching the communication agreement between the computer and PLC,this paper has finished setting up the communication between upper and lower computer,and also has described the method to compile computer monitoring program to realize the long-range monitoring and fault reporting for water supply system through communication modular.