Sunday, December 10, 2023

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Power Factor

Power Factor (Pf) can be calculated by dividing Kilowatts (KW) by Kilowatt-Amperes (kVA)

Pf = kW/kVA

Power factor is also related to power (W), current (I) and voltage (V) in single-phase circuits

I = W/ V x pf
E = W / I x pf
W = V x I x pf
PF = W / E x I

Please note that in the formula alone, the uppercase letter "W" is used to represent Power, which is measured in terms of Watts. The same uppercase "W" is also to mean Watts. Thus, the expression KW means kilo-watts. Sometimes the uppercase letter "P" is used to represent Power as well. It is a good practice to understand the context, problem or statement first, before determining the meaning of a variable or expression.

Example: What is the actual load (watts) of the circuit below?

W = V x I x Pf
W = 110V x 20A x .85
W = 1,870 W or 1.87 KW

Recall "k" stands for kilo, and it means one-thousand, therefore to go from W to KW, divide W by 1,000.


The following table shows some typical Power factor

Incandescent Lamps 1.0
Fluorescent Lamps (comp) 0.93
Ovens with Resistances 1.0
Dielectric Heating Ovens 0.85
Arc Furnaces 0.85
On an electrical contractor's test, you will be given the factor, no need to memorize any of them.

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