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Joined: Feb 2012
Posts: 1
D
New Member
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?

Joined: Dec 2002
Posts: 205
G
Member
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.

Joined: Jul 2004
Posts: 9,677
Likes: 9
G
Member
Is it getting plenty of air? These things, in confined space, can heat up quickly.


Greg Fretwell
Joined: Apr 2002
Posts: 7,288
Likes: 4
Member
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.


John
Joined: Feb 2004
Posts: 1,438
Member
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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