基于S7-200和MM440的变频恒压供水系统设计

针对过去带恒定转速泵供水系统的缺点，设计了一种利用S7-200PLC和变频器MM440的变频恒压供水系统，介绍了供水系统的基本特性、构成和工作原理，具体分析系统的主电路、控制电路和软件设计。实验效果表明，这种变频供水系统不仅可以提高供水的稳定性和可靠性，减小了电机的冲击电流和启动能耗，而且能够准确跟踪系统给定的水压。

Design of Variable Frequency Constant Pressure Water Supply System Based on S7-200 and MM440

For the shortcomings of the water supply system with constant speed pumps in the past, the variable frequency and constant pressure water supply system with S7-200 PLC and MM440 is designed. The basic characteristics, the composition and working principle of the water supply system are introduced.The main circuit, control circuit and software design of the system are analysed. Experimental results show that the stability and reliability of the system are enhanced immensely, the motor impact current and the strarting energy consumption are reduced. The given water pressure of the system is followed with the real water pressure accurately.