From: "Bill Howatt"
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
Subject: Re: welding a transformer core
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Thu, 19 Dec 2002 09:40:25 -0500
NNTP-Posting-Date: Thu, 19 Dec 2002 09:45:17 EST
Organization: Bell Sympatico
"Barry Lennox" wrote in message
> On 18 Dec 2002 03:25:33 -0800, email@example.com (N. Thornton) wrote:
> >Barry Lennox wrote in message
> >> Sounds like some serious BS here. This seemed wierd as I have been
> >> using a rewound MOT for a welder, and it spends a fair amount of it's
> >> time with no or an insignificant load on it. I had never noticed any
> >> "frying" tendencies.
> >> Anyway as a sanity check, I took another at random (I have a very
> >> large pile of these, SWMBO reckons another microwave coming in the
> >> door will sink the house!) and ran it for 15 mins with no load and
> >> there is no significant heating that I can detect. When can I expect
> >> the frying?
> >I think some other explanation is more likely than BS. People
> >sometimes think if they get 2 different results on 2 different
> >occasions one must be BS, but IME the world tends not to be that
> >A useful question might be: how can we explain both being correct?
> >Regards, NT
> 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.
> 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.
> Barry Lennox
A transformer that frys at no load very likely has a shorted turn.