33)
Note that the above relation has been obtained using three
assumptions: (i) the primary resistance and current are small; (ii) the
same flux links both the primary and the secondary as very little flux
escapes from the core, and (iii) the secondary current is small If the transformer is assumed to be 100% efficient (no energy losses),
the power input is equal to the power output, and since p = i v,
ipvp = isvs
(7 34)
Although some energy is always lost, this is a good approximation,
since a well designed transformer may have an efficiency of more than
95% Combining Eqs