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power factor (PF)

The power factor (PF) is a measure of the inductive or capacitive load, which is expressed in the phase shift between current and voltage for sinusoidal voltages. Mathematically, it is the quotient of active power (P) and apparent power (S). This quotient is denoted by the Greek letter 'lambda' and corresponds to the cosine 'phi' between the two powers.

The power factor can take values between 1 and 0 depending on whether the load is a resistive load, a reactance, i.e. a purely inductive or capacitive resistance, or impedance, which consists of an effective resistance and that of a reactance. In the case of a purely resistive resistor, the voltage and current are in phase, it is an active power and the power factor is "1". This power factor occurs in electric heaters and incandescent lamps, among others.

Power vector diagram with active, reactive and apparent power.

Power vector diagram with active, reactive and apparent power.

If a phase shift occurs between the two quantities, then it is a reactance whose imaginary component determines the phase shift. If there is a phase shift of 90° between the two quantities, it is pure apparent power and the power factor is "0". Electrical devices with high inductive reactance include motors, transformers, relays, etc.

Power factor meter for capacitive and inductive power factors, photo:leybold-shop.com.

Power factor meter for capacitive and inductive power factors, photo:leybold-shop.com.

Power factor is a quantity that is important for the power consumption of power supplies. Power factor values can be measured with power factor meters. They show the capacitive and inductive deviations as cosine Phi. In addition to the power factor, there is also the reactive power factor. This corresponds to the sine 'phi' of the ratio between reactive power and apparent power. The reactive power factor is calculated from the ratio between reactive power and apparent power. A higher reactive power factor results in a lower active power factor.

Informations:
Englisch: power factor - PF
Updated at: 24.01.2022
#Words: 300
Links: power (P), phase shift, current, voltage, active
Translations: DE
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