Frequency-modulated pump

A frequency-controlled pump is one that uses a variable-frequency speed control system to regulate the pump’s flow rate or pressure. In other words, the supply frequency to the motor is adjusted in a closed-loop manner based on the pump’s flow rate or pressure. Of course, the control valve is kept fully open. To maintain high system efficiency, the supply frequency at the effective operating point should generally not be lower than 30 Hz.

It's very simple. Before the use of variable frequency speed control, the speed of the motor remained constant, and flow regulation was achieved by controlling the opening degree of the valve. The larger the valve is opened, the greater the flow rate; conversely, the smaller the flow rate. With variable-frequency speed control, the valve is required to be fully open, while the flow rate is controlled and adjusted by the speed of the motor. A higher rotational speed results in a larger flow rate. When starting a pump driven by an inverter, the DCS can send a preset signal to the inverter in advance, such as 30%, without having to wait until the flow rate stabilizes. This is because the inverter has a setting that causes its output voltage and frequency to increase gradually; once they reach 30% of the set value, it will operate smoothly automatically.

Affected by the efficiency of the water pump, the minimum frequency setting for inverters is generally 30 Hz; 25 Hz is also acceptable when necessary, as the efficiency of the water pump must remain above 40%. Therefore, this point needs to be taken into account when adjusting the speed of water pumps using frequency conversion.

It achieves speed control by adjusting the output frequency, thereby increasing the output pressure!