When I plugged in a 250VA load to the left transformer. I can smell something burning and the case is super hot.

What causes the burning smell? What part of transformer can produce burning smell?

And does it mean the transformer is already ruined? If one would continue using it.. maybe it can fail suddenly or does the burning not produce permanent damage?

Both are rated 500VA.. but I think the small one that has smell is not a real 500VA capacity transformer. It is inside a voltage regulator. Maybe a voltage regulator especially boost buck type doesn't need a full capacity transformer because it's only adding or subtracting some voltage?

  • 1
    1kg wood and 1kg rock weighs equally. Similarly two 250VA transformers should look almost same size. Your left trafo certainly cannot be 250VA. – soosai steven Oct 29 '18 at 13:14
  • 1
    @soosaisteven this person has been asking many questions. From that history we know the one on the left is an autotransformer. They can be smaller. / It is also a Cheese no-name brand, wheras the one on the right is a reputable maker (though still made in China). Both transformers are larger than 250VA. – Harper - Reinstate Monica Oct 29 '18 at 14:43
  • 1
    OP do you have a clamp ammeter? Can you measure current going into the primary? At 250VA it should be a tick over 1 amp. I wonder if it is not. – Harper - Reinstate Monica Oct 29 '18 at 14:45
  • Both are 500VA rated.. not 250VA. I said I plugged in 250VA to the left AVR (Automatic Voltage Regulator) and temperature kept increasing even above 60 Celsius. However, I noticed this only occurred when I used the 110V output (of the AVR). If I used the 220V output, temperature maintains at 40C. I guess this is because at lower voltage output of the left AVR and autotransformer. The current is greater and the small transformer winding is not designed for 110V output (with greater current)? Right? – Samzun Oct 29 '18 at 14:50
  • This guy is a scammer always asking more questions based on answers with no up votes a total waste of time. – Ed Beal Nov 22 '18 at 2:57

The burning smell is the insulation of the winding conductors burning and is generally indicative of irreparable damage. It may still function, for a while, but has been severely compromised. Further failure often results in flames...

  • What would result in flames.. is it the transformer or the load connected to it? For an autotransformer, a short in the primary or open in the secondary can result in the full voltage appearing in the secondary. So I guess the transformer itself would not end up in flames but only the load, right? The load is a 120v SPD and I guess the thermal fuse would engage before the MOVs end up in flames. I ordered an additional Belden strip and would plug it into 240v to see if the thermal fuse would just activate or the strip would end up in flames so I can gauge the worse case scenario. – Samzun Oct 29 '18 at 22:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.