The transformer’s voltage and current determine its kVA (kilovolt-amps) value.
Calculating KVA single and three-phase transformer ratings. Transformer ratings show their maximum load power.
The transformer’s kVA depends on its voltage and current.
Transformer ratings depend on phase count, main and secondary voltages, and currents.
Calculate single-phase transformer ratings using this formula:kVA = VxI/1000where V is the transformer’s primary or secondary voltage (volts) and I is its current.
To rate a single-phase transformer with 120 V primary voltage and 10 A primary current, multiply 120 x 10 and divide by 1000.
Results: 1.2 kVA.Use this formula to obtain three-phase transformer ratings: (√3 x V x I)/1000 = kVACalculate √3 (roughly 1.732), V (volts), and I (amps) on the transformer’s main or secondary side.
If a three-phase transformer has 480 V primary line-to-line voltage and 20 A primary line current, its rating may be calculated by multiplying √3 x 480 x 20 and dividing by 1000.
16.6 kVA result.Use internet calculators like this one to determine transformer ratings. Just enter the phases, voltage, and current to get the kVA rating.
This should explain how to determine kVA ratings for single-phase and three-phase transformers.
