Electrical Formulas

Delta Transformer Voltage Formula

Eline = Ephase

Ohm's Law

E = IR (E - Voltage; I - Current; R - Resistance)

Wye Transformer Voltage Formula

Eline = Ephase(sqrt3)

Delta Transformer Current Formula

Iline = Iphase(sqrt3)

Ohm's Law Power Formula

P = IE (P - Power; I - Current; E - Voltage)

Resistance in a Parallel Circuit

Rt = 1/(1/R1+1/R2+1/R3)

Voltage in a Parallel Circuit

Same across each branch of the circuit

Current in a Parallel Circuit

The sum of current across each branch of the circuit

Voltage Drop Formula (Three Phase)

VD = (sqrt3)KIL/Acmil (VD - Voltage Drop; K - Specific Resistance; I - Current; Acmil - Area measured in circular mils)

Voltage Drop Formula (Single Phase)

VD = 2KIL/Acmil (VD - Voltage Drop; K - Specific Resistance; I - Current; Acmil - Area measured in circular mils)

Voltage in a Series Circuit

Voltage is shared between components

Delta Transformer Apparent Power (kVA) Formula

kVAline = EI(sqrt3)/1000 kVAphase = kVAline/3

Wye Transformer Apparent Power (kVA) Formula

kVAline = EI(sqrt3)/1000 kVAphase = kVAline/3

Wye Neutral Return Formula

sqrt[a^2 + b^2 + c^2 - (ab) - (bc) - (ca)]

Resistance in a Series Circuit

total resistance = sum of individual resistances

Wye Transformer Current Formula

Iline = Iphase

Current in a Series Circuit

Same at all points