In a three-phase electrical system, power factor is a measure of the efficiency with which electrical power is being used. It is a dimensionless quantity that ranges from -1 to 1, representing the phase relationship between the voltage and current in the system. Power factor indicates how effectively the current flowing through the system is being converted into useful work (real power) and how much of it is being lost as reactive power.
There are two components of power in an AC circuit: real power (measured in watts) and reactive power (measured in volt-amperes reactive or VARs). Real power is the actual power that does useful work, such as providing energy for devices to perform tasks like heating, lighting, or mechanical work. Reactive power, on the other hand, is the power that oscillates between the source and the load due to the reactive components in the circuit, like capacitors and inductors. Reactive power doesn't perform any useful work but is necessary to maintain the electromagnetic fields in the circuit.
The power factor is the ratio of real power (P) to apparent power (S), where apparent power is the vector sum of real power and reactive power. Mathematically, power factor (PF) is expressed as:
Power Factor (PF) = Real Power (P) / Apparent Power (S)
Or, in terms of the phase angle (θ) between voltage and current:
PF = cos(θ)
A power factor of 1 (or unity) means that the current is perfectly in phase with the voltage, indicating efficient utilization of electrical power. A power factor of 0 means that all the power is reactive power, indicating no real power being used for useful work. A power factor between 0 and 1 indicates a combination of real and reactive power.
Power factor correction is often employed in industrial and commercial applications to improve the power factor and reduce the amount of reactive power drawn from the electrical grid. This helps to improve overall system efficiency, reduce energy costs, and minimize losses in transmission and distribution systems.