Power Factor Explained

What is Power Factor?

Power Factor is the ratio of actual power (kW) to apparent power (kVA) in an alternating current circuit, represented as a decimal number between 0 and 1.

Power Factor can also be represented by thinking of a simple clock face, where a PF of 1 is represented by 12 o'clock. A PF of 0 can be either side of 12, either at 9 or 3 o'clock (depending on which way the kVArs are flowing in reference to the kW). The number isn't signed and is usually accompanied by leading or lagging. i.e. the current is leading or lagging the voltage. PF is caused by kVArs which are signed. When a generator is producing (positive) kVArs the load is inductive, such as a motor, and thus the current is lagging the voltage. Terms used to explain this are inductive, lagging and over excitation. When a generator is absorbing (negative) kVArs the load is capacitive such as fluorescent lighting and long cable runs, and thus the current is leading the voltage. Terms used to explain this are capacitive, leading and under excitation.

If the generator is feeding a purely resistive load, such as a heating element, there are no kVArs, and the PF is 1, also known as unity. This is when kW (real power) is equal to kVA (apparent power).

Power Factor Formula

PF can be calculated using the following formula: PF = kW / kVA

Power Factor Calculator

Use our handy calculator below to quickly calculate power factor using the kW & kVA values:

For more information, or to discuss your power requirements with our team of experts, call us on +44 (0) 1977 657 982 or email us at enquiries@ade-power.com.

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Blog published by ADE Power on August 14th, 2018

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