From: John Woodgate
Subject: Re: welding a transformer core
Date: Thu, 19 Dec 2002 14:38:57 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Thu, 19 Dec 2002 16:53:42 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Barry Lennox
wrote (in <57030vsr5p4go9elnd9leoioc755od
email@example.com>) about 'welding a transformer core', on Thu, 19 Dec 2002:
>Yes, I agree, anyway, I ran another 6 MOTs all different, with no load
>for 20 mins apiece, some run a little warm, the highest gaining about
>20 deg C in that time. Others barely increase at all. There is a (very
>rough) inverse correlation between temp rise and core size, but I'm
>sure that's not the sole connection.
If they are all of the same power rating, core size is, fundamentally,
the main factor in determining temperature rise. Your unit that rose 20
degrees in 20 minutes was almost certainly still far from thermal
equilibrium and would have become much hotter if left running.
>There certainly is no sign of frying in minutes as you originally
>asserted. Can you tell us what sort of MOT did just that? I suspect
>there may have been another problem with that MOT, the no-load
>condition being a coincidental distraction.
The prospect of a shorted turn looms large. But others have reported
rapid heating, so presumably some designs do exhibit that effect.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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