基于PLC和变频技术的恒压供水系统设计

AbstractThis article combines the basic situation of the water supply system in somecities in our country,and proposes a variable frequency and constant pressurewater supply system based on PLC control.The main components of the constantpressure automatic water supply system include:programmable controller,control box,frequency converter and sensor.In the constant pressure watersupply speed control system,the three water pumps use the frequency converterto set the power frequency f,so as to realize the engine speed control N,therebychanging the power curve of the water pump.The control unit of the variablefrequency technology automatic control system with constant water pressure ismainly developed from three stages,from relay to contactor to single-chipmicrocomputer,and then to the currently used PLC.At the same time,thefrequency converter is also controlled by speed control.Multiple ends of thespeed control are used for analog input control,and then reach the dedicatedfrequency converter.Due to the continuous improvement of regulators andfrequency converters,low-consumption urban water supply has become simpleand efficient,and the control process of the water supply system has also beenautomated.Use programming software to create a PID controller to control the pressurein the water supply system and integrate the PID controller into the PLC.Thecontroller can control the output frequency and voltage of the inverter in realtime by processing the actual measured pressure value and the deviation from theset value.The purpose is to change the speed of the pump motor and the flowrate at the outlet of the pump so as to automatically adjust the entire water supplypressure and keep the pressure close to the set value.