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#205512 - 02/28/12 07:36 AM dry type transformer failure
Danny00915 Offline
New Member

Registered: 02/23/12
Posts: 1
Loc: Singapore
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?

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#205526 - 02/29/12 12:18 PM Re: dry type transformer failure [Re: Danny00915]
geoff in UK Offline

Registered: 12/30/02
Posts: 171
Loc: UK
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.

#205527 - 02/29/12 02:30 PM Re: dry type transformer failure [Re: Danny00915]
gfretwell Offline


Registered: 07/20/04
Posts: 9023
Loc: Estero,Fl,usa
Is it getting plenty of air? These things, in confined space, can heat up quickly.
Greg Fretwell

#205528 - 02/29/12 07:22 PM Re: dry type transformer failure [Re: Danny00915]
HotLine1 Offline


Registered: 04/03/02
Posts: 6791
Loc: Brick, NJ USA
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.

#205555 - 03/03/12 02:31 PM Re: dry type transformer failure [Re: Danny00915]
Lostazhell Offline

Registered: 02/21/04
Posts: 1248
Loc: Bakersfield, CA (Originally Or...
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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