Transformer - KVA Rating & Load Calculation

I am here explaining how to calculate the Ampere/Load Capacity of a Transformer from given Parameters.

A you know, the Transformers ratings are generally displayed only in KVA / MVA ratings and its Primary/Secondary Voltages. Inorder to find out the Primary nd Secondary currents please follow the below steps.

Formulae to be Remembered 

P = (Root 3) X V X I   
                       (In gen case, we are not considering Power Factor for Transformers)
P = 1.73 X Primary V X Primary I
P = 1.73 X SecondaryV X SecondaryI


           Mva/Kva                    =    Primary Current
   1.73 X Primary Voltage

           Mva/Kva                     =   Secondary Current
1.73 X Secondary Voltage


Lets Assume a Transformer with following Paramateres

100Kva     11KV/415V


From  Example :-


          100,000                   =  5.25 Amps  (Primary Current)
      1.73 X 11,000

          100,000                   =  139.28 Amps  (Secondary Current)

      1.73 X 415

So the Secondary side have a capacity of 139.28 Amps which can feed a maximum load of 100KW (through its total of 3 Phase ).