how to size a breaker for a 3 phase transformer?

To size a breaker for a three-phase transformer, first determine the transformer’s full-load current using the formula: I = (kVA � 1000) / (?3 � V), where kVA is the transformer rating and V is the line voltage. Next, apply a safety factor, typically 125% of the full-load current, to account for inrush and overload conditions. Finally, select a breaker that matches or exceeds this calculated value, ensuring it meets local codes and standards.