Amps to kVA Conversion Formula, Example Problem

Single phase amps to kVA calculation formula

The apparent power S in kilovolt-amps is equal to current I in amps, times the voltage V in volts, divided by 1000:

S_(kVA) = I_(A) × V_(V) / 1000

Three phase amps to kVA calculation formula

Calculation with line to line voltage

The apparent power S in kilovolt-amps is equal to phase current I in amps, times the line to line RMS voltage V_L-L in volts, divided by 1000:

S_(kVA) = √3 × I_(A) × V_L-L(V) / 1000 

Calculation with line to neutral voltage

The apparent power S in kilovolt-amps is equal to phase current I in amps, times the line to neutral RMS voltage V_L-N in volts, divided by 1000:

S_(kVA) = 3 × I_(A) × V_L-N(V) / 1000

Where,

• S = Apparent Power in Volt-Amps

• V = Voltage in Volts

• I = Current in Amperes

• V_L-L = Line to Line Voltage in 3-Phase Circuits

• V_L-N = Line to Neutral Voltage in 3-Phase Circuits

Example Problem

Find the kVA rating of a single phase transformer if the primary current rating is 120 amperes and RMS voltage is 120V.

Solution:

S = (120V x 125A) ÷ 1000

kVA = S = 15kVA

Three Phase Amps to kVA Calculation

Calculation with Line to Line Voltage

Apparent Power in kVA = (√3 x Voltage in Volts x Current in Amperes) ÷ 1000

S = (√3 x V_L-L x I) ÷ 1000

Example:

Calculate the apparent power in kVA if the value of current is 28A and RMS voltage is 208V (line to line) three phase.

Solution:

S = (1.732 x 208V x 28A) ÷ 1000

kVA = S = 10kVA

Calculation with Line to Neutral Voltage