Power Factor Controller: Working Principle, Advantages, Basics

In today’s complex energy world, the reactive loads on a network continue to increase. The increase in the power on transformers, transmission lines, and generators caused a rise in reactive power. The control of the reactive loads has become a necessity and the power factor controller has played an important role in reactive power correction systems.

Before understanding the controller you should understand what reactive power is.

Reactive power is required by many loads to provide magnetizing current for motors, power transformers, welding machines, electric arc furnaces, inductors, and lighting ballasts. It is not a useful power and it should be controlled. It is clear that the utility must generate, transmit, and distribute both active and reactive power. But, if reactive power could come from another source, the utility can produce cleaner energy.

At that point, to control the reactive power automatically, we need capacitor banks and a power factor controller. The power factor controller is a complex device but I am going to explain to you the functions as much as simple. First, let’s start with the definition.

What is a Power Factor Controller?

The power factor controller (PFC) is the control unit of an automatic capacitor bank system. It performs the switching of capacitors to reach a user-defined target cos ɸ. With the integration of a power factor controller, it is possible to optimize processes, speed up troubleshooting and reduce the costs of the supervised systems.

Power factor controllers monitor the reactive power of a plant and try to match the power factor value which is defined as the ratio of the active power (W) to the apparent power (VA) to a value that is defined on the device by the end-user. It features a user interface with a menu-driven display in plain text for maximum ease of operation. Display of various grid parameters, storage of various values, and a test run option make it easy to analyze errors and monitor the system.

Power Factor Controller Working Principle

The power factor controller permanently monitors the reactive power of the installation and controls the power factor. The control is done by connecting and disconnecting the power capacitor banks. When the power factor decreases, the controller activates the capacitors sequentially.

If the power factor is less than the approved value, the microprocessor of the controller produces a command to turn on the relay. Turning on the relay will add a capacitor group to the circuit and improve the power factor. (Capacitors add reactive load to the circuit which will help to increase the power factor.) The controller will continue to add capacitors in parallel to the load until a good value of the power factor is attained.

In addition to power factor correction, it indicates electrical parameters such as current, voltage, power, energy, demands, and maximum/minimum values. It’s like the brain of the power correction system.

Advanced PFCs have “sequential connection” and “loop connection” features. In sequential connection, the required capacitor stages are successively connected and disconnected in stages (last in – first out). The ranking of each step always corresponds to the power of the smallest stage. In loop connection, the controller operates in loop mode (first in – first out) which minimizes the wear on the capacitor bank, i.e. where stages are of equivalent dimensions, the stage which was disconnected for the longest period of time is always connected next.

If you want to select a power factor controller for your applications you should consider the below parameters: