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Posted By: Danny00915 dry type transformer failure - 02/28/12 03:36 PM
I have a 50kVA dry type transformer which had failed, with rating:

1. Input (LV, primary winding): 400V, 72.17A
2. Output (HV, secondary winding): 21.5kV, 1.34A

The failed area was found to be the HV winding, where short circuit of winding and sign of local overheating was observed . Calculations showed no overload to input or output.

What would have cause the overheating? probable cause of the failure?
Posted By: geoff in UK Re: dry type transformer failure - 02/29/12 08:18 PM
Simple transformer insulation failure? It only takes one turn to short out and rapid overheating follows causing progressively more insulation failure.
Possible causes? Weak insulation since manufacture, moisture ingress, vibration, transient voltage surge, hotter than designed operating environment, - I'm sure there are more I can't just think of.
Posted By: gfretwell Re: dry type transformer failure - 02/29/12 10:30 PM
Is it getting plenty of air? These things, in confined space, can heat up quickly.
Posted By: HotLine1 Re: dry type transformer failure - 03/01/12 03:22 AM
100% agree with that Greg> I remember a plant where some employees used a 75KVA for a lunch warmer with help from some cardboard & welding screen curtains! A situation that could have become a njghtmare.
Posted By: Lostazhell Re: dry type transformer failure - 03/03/12 10:31 PM
We had an old Westinghouse padmount 12kv pri 480V sec 1000kva that inadvertently was loaded up with >1600 hp in oil pumping units & steam genset pumps & blowers.. It ran this way for quite some time & wasn't discovered until we ran into some low voltage issues in a control room... The load was divided up with 2 banks of 167s added. The padmount still runs part of the field..
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