Hi friends, I got a question, What is the best load that should be applied to a distribution transformer for maximum efficiency. The question also includes if there are 3 DTs of 100KVA operating in parallel. then if one get failure then how much load sharing should be given to the rest 2DTs for safe running..and what factors should be taken care of...Please suggest...Pulak

 

If this is homework I can move it for you.

With audio/rf applications load matters (where you are dealing with constant impedance), with power transformers it doesn't. It has to do with maximum transfer of power.

 

I think most transformer efficiency/load curves are hump shaped?

At zero current there are still some iron losses, so efficiency is low at very low loads. Then at high load currents the copper I2R losses get larger.

And toroidal mains transformers may be quite different from EI transformers.

Here's a couple of quick charts from googling;

(1 = standard EI core, 2 = toroid core, quite efficient!)