What is a power factor?

Answer 1

The Power Factor is an indicator of the quality of design and management of an electrical installation. It relies on two very basic notions: active and apparent power.

The active power P (kW) is the real power transmitted to loads such as motors, lamps, heaters, and computers. The electrical active power is transformed into mechanical power, heat or light.

In a circuit where the applied r.m.s. voltage is Vrms and the circulating r.m.s. current is Irms, the apparent power S (kVA) is the product: Vrms x Irms.

The apparent power is the basis for electrical equipment rating.

The Power Factor λ is the ratio of the active power P (kW) to the apparent power S (kVA):

The load may be a single power-consuming item, or a number of items (for example an entire installation).

The value of power factor will range from 0 to 1.

Answer 2

Asking "What is the use of power factor?" is a bit like asking "What is the use of poor eyesight?". It is is an undesirable state of affairs which should be corrected to make it closer to full efficiency.

Having to use a device having a poor power factor - without doing anything to correct it - is very similar to a person who has poor eyesight who is trying see properly without using the correct eyeglasses!

The power factor of a device is what determines how much useful power is used out of the total amount of power which is supplied to it from the source.

A power factor as close to 1 as possible is desirable because then most of the power transferred from the source to the load is useful power.

1. If a device has a power factor much less than 1, that means more total input current must be supplied for a given output power dissipation and a more powerful source is required to deliver the required output power. This means the device must draw a higher amount of volt-amps (VA) compared to the actual load power it is delivering, which means its conversion of input power VA to output power VA is inefficient.

2. The closer to a power factor of 1 that a device has, the better the total current which has to be supplied will match the output from the device, and the more efficient it will be in its conversion of input power VA to output power VA.

For more information see the Related Link shown below.

Answer 3

By definition, power factor is the cosine of the angle by which the load current lags or leads the supply voltage in an AC circuit. It is also the ratio of true power to apparent power. A lagging power factor occurs in an resistive-inductive circuit, where the load current lags the supply voltage. A leading power factor occurs in an resistive-capacitive circuit, where the load current leads the supply voltage

Answer 4

In alternating-current power transmission and distribution, the cosine of the phase angle between the voltage and current is called Power Factor.