摘要： 本论文基于高层供水的要求，设计一个基于西门子S7-1200 PLC的变频恒压供水系统，该系统由可编程控制器核心、调速变频器、供水水泵机组、水压传感器等构成。其中，系统包括两组水泵机组，每组包括三台水泵电机，两台处于工频或变频运行，一台用作后备使用。两组水泵电机均采用变频器实现软启动和调速，且每组水泵电机的工作时间要求相同，自动运行时采用变频循环的运行方式，每组内水泵电机在运行切换时采用“先启先停”的原则。水压传感器负责将供水管网的水压信号反馈给PLC，经过PLC处理后通过控制变频器输出的电压和频率，来调节水泵电机的转速或加减运行中的水泵电机个数，进而改变水泵出水口处的流量大小，实现变频恒压供水。每组内的电机可以根据实际需求进行自动切换，也可以单独启动每个水泵电机，可以进行手动控制，便于后期对系统的维护和调试。71105

毕业论文关键词：恒压供水；变频器 ；PLC；软启动

Design of Soft Starter Base on PLC Water Supply System

Abstract: The high-level water supply based on the requirements of the design based on SIEMENS S7-1200 PLC frequency constant pressure water supply system, the system consists of a programmable controller, inverter, speed core water pumps, water pressure sensor. Among them, the system consists of two sets of water pump units, each group consists of three pump motors, two units in power frequency or frequency conversion operation, and one is used as back-up. Two sets of pump motor adopts frequency converter to realize the soft start and speed, and each pump motor working time requirements are the same, the automatic operation operating mode with frequency conversion cycle, each pump motor adopts "start first stop first" principle in the operation of switching. The pressure sensor will be responsible for the water supply network hydraulic pressure signal feedback to the PLC, after the processing of the PLC through the inverter output voltage and frequency control, the number of pump motor speed or operation to adjust the pump motor and the outlet of the water pump, and then change the size of the flow of the constant pressure water supply. The motors in each group can be switched automatically according to the actual demands, and each pump motor can also be started separately. The manual control can be carried out to facilitate the maintenance and debugging of the system in the later stage.

Keywords: Constant Pressure Water Supply; Frequency Converter; PLC; Soft Start

目录

摘要 ii

Abstract iii

目录 iv

1 绪论 1

1.1 课题的研究背景和意义 1

1.2 变频恒压供水概论 1

1.3 变频恒压供水的发展现状 2

1.4 本论文主要设计内容 3

2 变频恒压供水系统的相关理论分析 4

2.1 水泵的工作原理 4

2.1.1 离心泵的结构 4

2.1.2 离心泵的工作原理