Re: No-load losses for distribution transformers?

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Spir Georges GHALI

Ldscp said:

Trying to get approximate numbers for core/iron/parasitic losses in large (50-500 kVA) distribution transformers that might serve one light-industrial building or complex, taking 13,800V to 480V 3-phase.The application is very low duty-cycle, so unloaded losses will dominate.

Have spent quite a bit of time browsing the Web; most postings either talk about standards or promote advanced tech that may not be in service yet.

Is there a general guideline our group might use?

Thanks very much for all advice.



Dear Mr. Mike ;


As I don't use these special Voltages, I can give you an idea about that I used for some special applications where the Voltages are ” 13.2 KV  &  420 V ” and the manufacter is ” Zucchini – Italy “.

– 100kVA : Po : 380W,     Pt(+70°C) : 1800W

– 160kVA : Po : 480W,     Pt(+70°C) : 2550W

– 250kVA : Po : 750W,     Pt(+70°C) : 3120W

– 315kVA : Po : 1050W,     Pt(+70°C) : 4050W

– 400kVA : Po : 1320W,     Pt(+70°C) : 5000W

– 500kVA : Po : 1630W,     Pt(+70°C) : 5960W

Where :

     – Po : the Losses without load

     – Pt(+70°C) : the losses with ful load at ” +70°C “