Energy saving and control methods of frequency converter

There are two control modes for frequency converters in actual use:

(1) Open-loop control is applicable to constant speed and constant output conditions. The open-loop control circuit is simple and cost-effective, as shown in the figure below.

(2) Closed-loop control is applicable to conditions of variable speed and output, as shown in the figure below.

This system needs to add sensors and PID regulators. Although the installation cost is higher, it is beneficial to improve the control accuracy. The control accuracy is ≤0.1%. In situations where precise control of temperature, pressure, flow, speed, tension, position, pH value, etc. is required, closed-loop control is generally used to implement fixed value control. Under the same working conditions, closed-loop control can save 5% to 10% more electricity than open-loop control.