2. Single phase Single-Phase Power For a transformer the power-factor of the load is not known, therefore the formula becomes: Volt-Amps For a Power Transformer Therefore the Secondary Full Load Current Prospective Fault Current Example 1 Consider a 2 kVA 230 V /32 V single-phase transformer with an impedance voltage of 11.5 V The percentage Impedance Full Load Current Prospective Fault Current