Page 585 - Basic Electrical Engineering

maximum efficiency is

Example 6.13 Efficiency of 400/200 V, 200 kVA transformer is 98.5 per

cent at full load at 0.8 lagging power factor. At half load, 0.8 power factor
lagging the efficiency is 97.5 per cent. Calculate the values of core loss and

full-load copper loss.

Solution:

Let W be the core loss and W be the full-load copper loss.
c
cu

or,

W + W = 2.43 kW = 2430 W (i)
cu
c
At half load, W will remain the same but W will be one-fourth its full-load
cu
c
value. Efficiency at half load is

or,