ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

ECN Shout Chat
Top Posters(30 Days)
Admin 19
Recent Posts
fuse rejectors
by NORCAL. 03/29/17 01:44 AM
Old decora style outlets
by NORCAL. 03/29/17 01:41 AM
NFPA stuff
by gfretwell. 03/28/17 08:08 PM
Anyone hiring inspectors?
by HotLine1. 03/27/17 08:03 AM
ESA Arc flash course
by TheShockDoctors. 03/24/17 10:15 AM
New in the Gallery:
SE cable question
Popular Topics(Views)
231,854 Are you busy
166,738 Re: Forum
160,865 Need opinion
Who's Online Now
0 registered members (), 79 guests, and 11 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#205512 - 02/28/12 11:36 AM dry type transformer failure  
Danny00915  Offline
New Member
Joined: Feb 2012
Posts: 1
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?


Work Gear for Electricians and the Trades

#205526 - 02/29/12 04:18 PM Re: dry type transformer failure [Re: Danny00915]  
geoff in UK  Offline
Member
Joined: Dec 2002
Posts: 180
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 06:30 PM Re: dry type transformer failure [Re: Danny00915]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,060
Estero,Fl,usa
Is it getting plenty of air? These things, in confined space, can heat up quickly.


Greg Fretwell

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


Member
Joined: Apr 2002
Posts: 6,803
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.


John

#205555 - 03/03/12 06:31 PM Re: dry type transformer failure [Re: Danny00915]  
Lostazhell  Offline
Member
Joined: Feb 2004
Posts: 1,428
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..



Member Spotlight
noderaser
noderaser
Portland, Oregon, United States
Posts: 404
Joined: March 2007
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.013s Queries: 15 (0.003s) Memory: 0.7669 MB (Peak: 0.9103 MB) Zlib enabled. Server Time: 2017-03-30 12:44:20 UTC