From: John Woodgate
Subject: Re: 2.5kW-3kW-SMPS-(cheap)-suggestions?
Date: Tue, 17 Dec 2002 22:40:06 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Tue, 17 Dec 2002 23:20:51 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that John Jardine
wrote (in ) about '2.5kW-3kW-SMPS-(cheap)-suggestions?', on Tue, 17 Dec 2002:
>Yes. Some heater systems can and do use 110V (or 220V) direct. So the PSU is
>simply a relay and timer (oh! if they were all 110V :-). Others have more
>precise needs which throws complexity onto the power supply. Hence the 3kW
OK, but there's 'complexity' and 'five-dimensional chess'. (;-) Since
the wires are 'fine', there must be some sort of paralleling to get the
whole thing to take 55 A. Changing to a different network should get to
a 110 V rating without changing so very much as far as the heating
effects are concerned.
As a thought-experiment, cut a heater network in half and wire the two
halves in series. You now have four times the original resistance. Apply
double the original voltage. Power = V^2/R, and (2V)^2/4R = V^2/R, so
the heating effect is the same.
Think of the time, effort and money you'd save if you could get the
heaters made that way!
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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