ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Violation?
by renosteinke - 01/27/23 09:52 PM
Does NEC 551.71 (F) apply to dwellings?
by BigB - 01/20/23 10:46 AM
Power submeter connections
by HotLine1 - 01/19/23 09:09 AM
AFDD's coming to the UK
by Texas_Ranger - 01/17/23 07:22 PM
New in the Gallery:
Burger King crown sillyness
Burger King crown sillyness
by wa2ise, December 11
240/208 to a house
240/208 to a house
by wa2ise, October 9
Who's Online Now
1 members (gfretwell), 52 guests, and 12 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
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: 206
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: 9,788
Likes: 14
G
Member
Is it getting plenty of air? These things, in confined space, can heat up quickly.


Greg Fretwell
Joined: Apr 2002
Posts: 7,333
Likes: 7
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..


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *
2023 National Electrical Code (NEC)
2023 NEC Now Available!
 
* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
CDS
CDS
Nicholson Ga
Posts: 34
Joined: June 2006
Top Posters(30 Days)
BigB 9
triple 3
Popular Topics(Views)
302,487 Are you busy
231,878 Re: Forum
216,501 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5