We have selected an 800 kVA oil cooled transformer.The ECBC table of transformer losses does not have specific allowable losses for 800 kVA units. What options are available to us to get maximum allowable power transformer losses for this particular case?

The following method of extrapolation should be used to calculate the losses of a transformer at 50% and 100%.

 If a project is going to install a 800kVA transformer then in that case the calculation for 100% losses will be as following:

  1. Values prescribed by ECBC for transformer above and below the required one i.e. 800 kVA:

630kVA lower value losses at 100% 6.64

1000kVA upper value losses at 100% 9.80


  1. Difference of 370kVA and 3.16 losses at 100% loading

3.16/370=0.0085 (losses per kVA)


  1. Now subtract the installation transformer capacity with the lowest provided in ECBC that is 800-630=170kVA


170x0.0085= 1.44


  1. Finally, add the losses given in ECBC for 630kVA and 170kVA.

6.64+1.44=8.085kW is the maximum allowable power transformer loss for the mentioned transformer.


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