Innovative Power Products Combiners / Dividers

Power Factor Equations

Power factor measures the phase angle between the instantaneous voltage and the instantaneous current in a circuit. Voltage (E) leads current (I) by 90° in an inductive (L) circuit and voltage (E) lags current (I) by 90° in a capacitive (C) circuit.

A popular mnemonic is ELI the ICE man since E is leading (coming before) I in ELI, and E is lagging (coming after) I in ICE.

power factor ( P_f ) = cos ( q )
Apparent Power ( P ) = I * V
True Power = P
I = Current
q = Phase angle
V = Voltage

Power Formulas

Apparent Power
P = I * V
P = I² * R
P = V² / R

True Power
P = I * V * cos (q)
P = I² * Z * cos (q)
P = V² * cos (q) / Z
P = P_a * P_f

Impedance
Z = V² * cos (q) / P
Z = P / [I² * cos (q)]

Current
I = P / [V * cos (q)]
I = sqrt {P / [Z * cos (q)]}

Voltage
V = P / [I * cos (q)]
V = sqrt [P * Z / cos (q)]

where

P = power in Watts
V = Voltage in Volts
I = current in Amps
R = resistance in Ohms (Ω)
Z = impedance in Ohms (Ω)
q = phase angle between I and V in degrees
P_a = apparent power in Volt·Amps (VA)
P_f = power factor




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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ... All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged. My Hobby Website: AirplanesAndRockets.com