Power Energy
Power Factor
Power factor is the ratio of active power to apparent power, equal to the cosine of the phase angle between voltage and current in a sinusoidal system. A power factor of 1 means all the apparent power is active power. Inductive loads such as motors operate at a power factor below 1, which means the supply must carry more current than the active power alone would require.
Power Factor
PF = P ÷ S = cos φ
Variables and units
| Symbol | Quantity | Unit |
|---|---|---|
| PF | Power factor | dimensionless |
| P | Active power | W |
| S | Apparent power | VA |
| φ | Phase angle between voltage and current | degrees or radians |
Conditions of application
Sinusoidal steady state. Power factor is between 0 and 1 for a passive load; a leading or lagging qualifier describes whether current leads or lags voltage.
Worked example
Solved
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