In a two winding 1-phase transformer on load,

Primary Current(I1) = No Load Current(Io) + Primary Counter Balancing Current(I2')

So, We get I1 = Io + I2'

We know I2' = K*I2, where K is the turns ratio

But some places, It's mentioned I2' = -K*I2 (Accounting to the 180 degree phase shift)

I am confused what to consider.


1 Answer 1


We know I2' = KI2, where K is the turns ratio*

No, that is incorrect.

The negative sign must be used if you want to be accurate because the two currents (I2' and I2) are certainly of opposite phase. If they weren't opposite in phase then, I2' wouldn't be a "counter-balancing current" and, the impact of this is that there would be significant flux in the core due to load currents.

This would lead to a massive increase in the secondary induced emf which, in turn would lead to even greater load currents and things spiral to infinity.


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