For simplicity, let us assume that the initial flux in the transformer core at t = 0 is .
Then, we can compute the flux in the transformer core by using Faraday's law, --- (2) (3)
Fig 7.5 shows the plot of the flux due to dc offset current as a function of time with . It can be seen that flux in the core increases exponentially to a peak value of
as , Since, maximum value of I0 is , it implies that
can be as high as
.
. 
--- (2) 
(3) 
as 
, Since, maximum value of I0 is 
, it implies that
can be as high as
. 
