Abstract : This paper presents the design of a variable frequency speed control scheme for a water supply system. Variable frequency speed control can achieve towerless water supply, and the relevant parameter settings and calculation methods are given. Variable frequency speed control is used in water supply systems and can achieve energy saving. Keywords : Variable frequency drive, closed-loop control, logic relay, energy saving 1 Introduction In water supply systems, user water consumption often varies randomly. If the number of pumps in operation and their speed are not adjusted accordingly, it will lead to energy waste during off-peak hours and damage to the pipeline network and its auxiliary equipment during periods of high network pressure. Variable frequency speed control, a microcomputer controller, and logic control elements can achieve constant pressure variable flow water supply. 2 Variable Frequency Drive Water Supply System Pressure sensors are installed on the user-end pipeline to detect the water pressure. The microcomputer controller compares the pressure setpoint with the network pressure measured by the pressure sensor, and the error signal is used as the speed setpoint for the variable frequency speed control. The variable frequency drive outputs a variable frequency electric motor to supply water to the pump, causing the pump speed to change accordingly, while ensuring constant network pressure. When the frequency is adjusted to 50Hz, it is equivalent to a short circuit in the frequency converter, and the water pump runs at full speed. The main control circuit for the water pump is shown in Figure 2. [b][align=center]For more details, please click: Variable Frequency Speed ​​Control Design of Water Supply Electrical Control Device[/align][/b]