For determination of distributed load on many parallel transformers with different rating power and impedance voltage, we can use following equations: S = Total load S1 = Rated KVA of TR.1 S2 = Rated KVA of TR.2 S3 = Rated KVA of TR.3 Uk=Resultant impedance of power transformers bank Uk1 = Impedance voltage of TR.1 Uk2 = Impedance voltage of TR.2 Uk3 = Impedance voltage of TR.3 S/Uk = S1/Uk1 + S2/Uk2 + S3/Uk3 The power assumed by the individual transformers is : Sa1 = S1. Uk/Uk1 Sa2 = S1. Uk/Uk2 Sa3 = S1. Uk/Uk3 For example: S1 = 3500 KVA , Uk1= %6 S2 = 2500 KVA , Uk2= %5 S3 = 1500 KVA , Uk1= %4 S = 6750 KVA We can write: Uk= 6750 /( 3500/6 + 2500/5 +1500/4) = % 4.63 Sa1 = 3500 x 4.63/6 = 2700 KVA Sa2 = 2500 x 4.63/5 = 2315 KVA Sa3 = 1500 x 4.63/4 = 1736 KVA > 1500 KVA (The individual transformer should not be subjected to overload) Transformer No.3 is thus overloaded, therefore we cannot transfer whole of actual load with three mentioned transformers. Available transfer load is: 2700 + 2315 + 1500 = 6515 KVA