Solution for Powtran Variable Frequency Drives in Water Treatment Plants-POWTRAN-Engaged in intelligent motor control products

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Solution for Powtran Variable Frequency Drives in Water Treatment Plants

2012-07-30

I. Overview of the Original Pump System:

In water supply systems, constant-pressure water supply refers to a control method in which the outlet pressure is maintained at a set value regardless of changes in water consumption within the distribution network, achieved by continuously monitoring the network pressure. Typically, when selecting pumps, the rated flow capacity of the equipment chosen exceeds the actual flow requirement. However, the actual water demand varies during operation—for example, in building water supply systems, water consumption fluctuates significantly between day and night. Therefore, it is common practice to use valves to regulate flow. Although this approach is simple, it essentially achieves regulation by artificially increasing resistance. Such throttling-based regulation methods not only waste substantial amounts of electrical energy but also lead to higher equipment operating and maintenance costs. This article introduces an automatic constant-pressure water supply control system that leverages the built-in PID function of the PI7800 frequency converter, thereby meeting the requirements for energy conservation and reduced consumption.

II. Inverter Solutions

The frequency converter is a control device for pump motors. It can supply the pump motor with frequency signals ranging from 0 to 50 Hz according to the constant water pressure requirement, thereby adjusting the motor’s rotational speed. The water pressure is detected by a pressure sensor installed on the main pipeline of the network and converted into a current signal ranging from 4 to 20 mA, which is then fed back to the frequency converter. Based on the set reference value and the actual feedback value (as provided by the IF feedback port at the frequency converter’s control terminal)—that is, the voltage setting corresponding to the desired constant pressure and the feedback current signal received from the pressure sensor—the frequency converter employs PID control to automatically adjust its output frequency, thus regulating the rotational speed of the controlled pump motor and ensuring that the network pressure remains consistently stable.

Figure (1) Production Line