Automatic Power Factor Corrector: Real-Time Capacitor Bank Switching
How an embedded power factor correction device monitors AC load behavior and switches capacitors to improve efficiency.
The problem
Low power factor is a common issue in AC loads, especially with motors and inductive equipment. It increases current, creates extra losses and can bring penalty charges in industrial settings. I built an automatic power factor corrector to understand this problem from measurement to control.
The device monitors the load condition and switches capacitor stages through relays. The target is to bring the power factor closer to unity without manual capacitor selection.
Measurement and correction
The system needs voltage and current information. From that, the controller can estimate the load behavior and decide how much capacitive correction is required. The capacitor bank is divided into stages, and relays connect or disconnect the stages.
This staged approach is practical. Instead of using one fixed capacitor, the system can respond to different loads.
Firmware logic
The firmware reads the measurement values, calculates the correction need, selects relay outputs and updates the display. A very important detail is relay timing. If the firmware switches too quickly, the system can chatter and reduce relay life.
So the control logic should include delay, threshold and stability checking. Power systems are not like button input. They need patient decisions.
Hardware lessons
Capacitor switching on AC lines needs safety consideration. Discharge paths, relay ratings, isolation, fusing and enclosure design are necessary for a real product. In the prototype stage, the main learning was how to combine measurement, decision and switching.
The display also makes the system easier to explain. People can see voltage, current, power and correction behavior instead of only hearing theory.
Why this project matters
This project connects classroom power theory with a working embedded device. It is also relevant for small factories, workshops and labs where electrical efficiency matters.
Future improvements can include a dedicated metering IC, RMS calculation, Modbus communication, data logging and a safer industrial enclosure. The project is a strong example of how embedded control can improve power quality.