You might have come across the term “Power Factor” or Power Factor Correction (PFC) when dealing with alternating current circuits. In simple terms, Power Factor (PF) is a ratio of the Real Power to Apparent Power within an AC circuit. Real Power (“mW”) is the amount of actual work done by a component over time, or equivalently, it is the product of Power (Watts) and Time (seconds). Power Factor (PF) describes the amount of real power in an AC circuit. Power Factor depends on the efficiency of a circuit’s components.
Apparent Power (“VA”) represents what your circuit loads seem to use at the wall. It is given by Power (Watts) multiplied by Voltage (Volts) divided by Current (Amps). The Power Factor is based on the true Power in a circuit, but is often confused with Apparent Power. Power Factor Correction tries to improve the Power Factor value of an AC circuit.
Power Factors can be calculated from two different perspectives: Power from the Power Factor and Power to the Power Factor. In a purely resistive circuit with Power Factor equal to 1 (1 PF) the Power is equal to the Apparent Power (“VA”). That means that real and apparent power are identical. We can calculate their values using algebraic equations or use an online calculator such as this one.
Note that Power Factor can be greater than or equal to 1 and less than or equal to 1.
A Power Factor of 0 means that Real Power equals Zero, but Apparent Power is still equal to the product of Power (Watts) and Voltage (Volts). This happens when there are reactive components in a circuit. Reactance (X) is the capability of a circuit to store and discharge energy in the form of an Alternating Current. Reactance (X) can be likened to resistance in the Direct Current (DC) world, except that it varies with frequency, not voltage. Power in an AC circuit can be found using Power Factor formulas for resistive (or purely reactive) and reactive Power in the Power Factor calculations.
Reactive Power is, as its name suggests, a Power type that only exists because of inductance and capacitance (Real Power). It can be found using Power Factor formulas for resistive (or purely reactive) Power in the Power Factor calculations.
Power factor formula for Inductive Power
The Power Factor of Power created by Inductance (L) is equal to the product of Power (Watts) and the square root of Voltage divided by Current:
Power factor formula for Capacitive Power
The Power Factor of Power created by Capacitance (C) is equal to the product of Power (Watts) and the square root of Voltage divided by Current:
Current Power Factor formula
The Power Factor of Power created by Inductance (L) is equal to the product of Power (Watts), Current (Amps) and the square root of Voltage:
Voltage Power factor formula
The Power Factor of Power created by Capacitance (C) is equal to the product of Power (Watts), Voltage (Volts) and Current: