From: John Woodgate
Subject: Re: welding a transformer core
Date: Tue, 17 Dec 2002 16:49:20 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Tue, 17 Dec 2002 17:41:30 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that N. Thornton
wrote (in ) about
'welding a transformer core', on Tue, 17 Dec 2002:
>Microwave transformers are inefficient. Run one with no load and no
>fan and it'll be fried in minutes.
It's not exactly inefficiency. They are designed to run a fixed load for
a few minutes. The no-load induction is well into the core saturation
region, so that iron losses are high. On load, the wiring is run at a
very high current density, so copper losses are high but iron losses are
a lot lower due to the demagnetization effect of the secondary current.
However, the rectifier is half-wave, so that there is d.c. induction in
the core as well.
What this boils down to is that the transformer will run hot UNLESS you
get the loading right.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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