Useful Formulas

Ohm’s Law:

V = I x R

I = V ÷ R

R = V ÷ I

Single-Phase AC Power:

P (watts) = V (volts) x I (amps) x Power Factor

Three-Phase AC Power:

P3∅ (watts) = V (volts) x I (amps) x Power Factor x 1.732

Power Factor:

PF = cosine (phase angle)

PF = Power (watts) ÷ [ V (volts) x I (amps)]

PF = Real Power (watts) ÷ Apparent Power (VA)

Apparent Power:

Apparent Power (VA) = V (volts) x I (amps)

Peak Voltage:

Vpeak = Vrms ÷ 1.414

RMS Voltage:

Vrms = Vpeak x 0.7071

Inductive Reactance:

XL (ohms) = 2 x π x ƒ x L

where XL is the inductive reactance, π is pi (3.14), ƒ is the frequency in hertz, and L is the inductance in henrys