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dry type transformer failure #205512
02/28/12 11:36 AM
02/28/12 11:36 AM
Danny00915  Offline OP
New Member
Joined: Feb 2012
Posts: 1
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?

Work Gear for Electricians and the Trades
Re: dry type transformer failure [Re: Danny00915] #205526
02/29/12 04:18 PM
02/29/12 04:18 PM
geoff in UK  Offline
Joined: Dec 2002
Posts: 186
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.

Re: dry type transformer failure [Re: Danny00915] #205527
02/29/12 06:30 PM
02/29/12 06:30 PM
gfretwell  Offline

Joined: Jul 2004
Posts: 9,187
Is it getting plenty of air? These things, in confined space, can heat up quickly.

Greg Fretwell
Re: dry type transformer failure [Re: Danny00915] #205528
02/29/12 11:22 PM
02/29/12 11:22 PM
HotLine1  Offline

Joined: Apr 2002
Posts: 6,936
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.

Re: dry type transformer failure [Re: Danny00915] #205555
03/03/12 06:31 PM
03/03/12 06:31 PM
Lostazhell  Offline
Joined: Feb 2004
Posts: 1,431
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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