United Arab Emirates University
Electrical Engineering Department
Electric Circuits II (ELEC 3252)

    Chapter 1

1.5 Power Factor



The power factor is a very important quantity. Its importance comes from the economic impact it has on industrial users of large amounts of power. The power factor (pf) is defined as the ratio of the average power to the apparent power.

Therefore, In general:



    1. The previous example clearly indicates the economic impact of the load's power factor. A low power factor at the load means that the utility generators must be capable of carrying more current at a constant voltage, and they must also supply for higher line losses than would be required if the load's power factor were high.

    2. The power factor is the cosine of the phase difference between voltage and current. It is also the cosine of the load-impedance angle.

    3. The apparent power (in VA) is the product of the rms values of voltage and current.

    4. Leading power factor means that current leads the voltage and lagging power factor means current lagging the voltage.


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