When the water consumption is large, the water pressure decreases and the inverter output frequency increases. When the inverter operating frequency reaches the upper limit and runs stably for 10s, if the pipe network pressure is lower than the water pressure set value at this time, increase No. 2 Water pump. Under the logic control of the PLC, the electromagnetic switch connecting the No. 1 pump motor and the inverter is disconnected, the No. 1 pump motor is switched to power frequency operation, and the inverter is connected with the No. 2 pump motor to make the No. 2 pump motor work in speed regulation. status.When the water consumption is small, the water pressure increases, the output frequency of the inverter decreases, and the pump reduction process is entered, and the speed of the water pump motor decreases. Press the set value and stop the water pump controlled by the inverter. If the No. 1 pump is running at the power frequency, switch the No. 1 pump from the power frequency operation to the variable frequency operation.