ARM(R) Microcontroller Based Automatic Power Factor Monitoring and Control System

Abstract

The project aims to build a simple, compact and energy-efficient system for automatic power factor monitoring and control. It incorporates Stellar is® ARM® Cortex-M3 based LM3S608 micro controller kit along with a zero crossing detector circuit and a relay driver circuit. Current transformer and potential transformer are used for gathering real time current and potential data. It is fed into the micro controller via a zero crossing detector built using TI OPA4277 High Precision Operational Amplifier. From the directly received phase data, micro controller calculates the phase difference and hence the power factor of the system. It is displayed on an HD44780 controlled 16x2 Liquid Crystal Display. According to the current power factor, capacitors are automatically switched into the circuit using relays to bring the power factor close to unity. The relay driver circuit is built using TI ULN2003A IC. The system has been tested on different loads. Power factor is accurately displayed and brought close to unity. The use of ARM® based 32-bit micro controller promises extension of the project to a complete power management unit. Apart from lower power consumption, it allows easy extension of functionalities from power data logging, remote monitoring and control, emergency alarm etc.