Power factor
In electricity, the power factor (PF or cosφ) is the ratio between the power that can be used in electric circuit (real power, P) and the power from the result of multiplication between the current and voltage circuit (apparent power, S). The power factor is defined as:
- [math]\displaystyle{ \frac{P}{S} }[/math]
PF ranges from zero to one. The higher the PF, the more efficient the circuit is because more power can be used, and vice versa. Factors that can cause PF to be less than one is non-linear load, which are capacitive load and inductive load.
Power Factor Media
Schematic showing how power factor is calculated
Instantaneous and average power calculated from AC voltage and current for a load with a lagging power factor (ϕ = 45°, cos(ϕ) ≈ 0.71). The blue line (instantaneous power) shows that a portion of the energy received by the load is returned to the grid during the part of the cycle labeled ϕ.
The power triangle shows the relationship between real, reactive, and apparent power, and how these three components relate to the power factor.
Diagrams showing examples of lagging and leading power factors.
Power factor correction of linear load
1. Reactive power control relay; 2. Network connection points; 3. Slow-blow fuses; 4. Inrush-limiting contactors; 5. Capacitors (single-phase or three-phase units, delta-connection); 6. Transformer (for controls and ventilation fans)
Sinusoidal voltage and non-sinusoidal current give a distortion power factor of 0.75 for this computer power supply load.
Specifications taken from the packaging of a 610 W PC power supply showing active PFC rating
75 MVAr capacitor bank in a 150 kV substation
