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Minimum power loss in a transformer

Minimum power loss in a transformer

Minimum power loss in a transformer


We need to order a transformer 5 MVA 22kV/11 kV Copper windings. The quote we have received has no load losses 3.71 kW , power loss at full load 75 deg C 45 kW. Is it possible to have a transformer with lower power losses? What are the latest regulations/Standards levels for transformer power loss? Thks

RE: Minimum power loss in a transformer

You do realize that's a 0.9% full load loss, right? How much more efficient than 99.1% do you expect?

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RE: Minimum power loss in a transformer

You can always ask for a higher efficient transformer but be aware that it's cost will increase aswell, maybe considerably.

I don't have USA references in this case (DOE 2016 does not apply here), but for your information, in IEC world (IEC 60076-20: Power transformers - Part 20: Energy efficiency) your transformer surpasses the IEC level 2 efficiency (high energy performance):

PEI IEC level 2 for 5000 kVA (table 8): 99.387 %
PEI of your transformer: 99.488 % approx.

PEI being Peak Efficiency Index, maximum value of efficiency at the load factor when no load losses equals load losses.

So its not a bad efficiency for you after all.

Hope it helps.

RE: Minimum power loss in a transformer

We normally do not specify losses. We calculate how much the losses cost over the life of the transformer and use that to evaluate the bid cost. The manufacturers can design the transformer to provide losses that minimize the evaluated cost.

RE: Minimum power loss in a transformer

Transformer total price includes copper part price and steel core part price. One may increase the copper volume and reducing the core volume or vice-versa in order to achieve the minimum price. In the same time the losses are limited by bid requirement and the deviation- in the case of increased losses than required-will be permissible by total price reducing.
For instance, in one bid there is a formula how to calculate the price:

RE: Minimum power loss in a transformer

Thks for the info

RE: Minimum power loss in a transformer

Thks for the link

RE: Minimum power loss in a transformer


We have received quotes for a spare transformer

Quote 1 no load loss 3.424 kW loaded loss at 75 deg C 37.37 kW Price Rs 3.2m
Quote 2 no load loss 5 kW loaded loss at 75 deg C 30 kW Price 3.9m

Can Quote 2 losses be correct ? higher no load loss but lower loaded loss
The transformer will be in service 24/7. Cost of kWh is Rs 2.97. For 1 year, the difference of 7.37 kW in higher loaded loss will cost Rs 191 747, assuming that the transformer is fully loaded.

So Quote 2 seems to be better although the price is higher. With Quote 2, after 3.65 years we will recover the saving in lower price due to lower full load losses, assuming the 30 kW is correct.
Is this reasoning correct? Please advise.

RE: Minimum power loss in a transformer

You can have one transformer with lower no-load losses and higher load losses.

Are the transformers fully loaded 24/7? If not, you have to consider the load and loss factor. Consider that load losses are proportional to the square of the load current. It may be that the higher no load loss of Quote 2, that applies 24/7, outweighs the lower load loss.

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