Understanding How to Calculate Transformer Power for Single and Three-Phase Systems

Transformer power is calculated using the formula: output voltage × output current. For single-phase transformers, the power is determined by multiplying the total power consumption by 120%, assuming an 80% efficiency rate. When dealing with three-phase systems, such as a setup with a phase voltage of 220V and line voltage of 380V, the rated power can be calculated as 1.732 × rated current × rated line voltage. For uneven phase loads, like 9KW on phase A, 10KW on phase B, and 11KW on phase C, the total power is 33KW. Factoring in a power factor of 0.8, the transformer’s total power becomes 41.25kW.