First, start the motor of the No. 1

First, start the motor of the No. 1 water pump to work in the state of speed regulation. When the operating frequency of the inverter reaches the upper limit and runs stably, if the pipe network pressure is lower than the set value of water pressure at this time, add 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 supply pressure is greater than the set value, it needs to enter the process of reducing the pump. At this time, the output frequency of the inverter decreases, and the speed of the water pump motor decreases. When the output frequency of the inverter reaches the lower limit and runs stably for a period of time, the water pump controlled by the inverter is stopped. If both water pumps are running at this time, reduce the No. 2 water pump, and make the No. 1 water pump motor work in the speed control state. Otherwise, the No. 1 water pump stops. If the pipe network pressure is still greater than the set value, stop.