This document discusses calculating values for a three-phase power transformer. It provides the formula for determining the volt-amps for a three-phase power transformer when the load power factor is unknown. As an example, it calculates the full load current and prospective fault current for a 300kVA, 11kV/415-240V three-phase distribution transformer with 5% impedance.

1. Three-phase transformer Three-Phase Power For a transformer the power-factor of the load is not known, therefore the formula becomes, Three-Phase Volt-Amps For a Power Transformer Therefore the Secondary Full Load Current Prospective fault current

2. Example 2 Consider a 300 kVA, 11 kV/415-240 V three-phase distribution transformer with a percentage impedance of 5% Full Load Current = 417.4 A Prospective fault current