On Jul 12, 2:29 pm, "Paul E. Schoen" <pst...@[EMAIL PROTECTED]
> wrote:
> <mrdarr...@[EMAIL PROTECTED]
> wrote in message
>
>
news:0631a23f-0a93-4a34-a703-b3bd4e22ba06@[EMAIL PROTECTED]
>
>
>
> > On Jul 12, 7:40 am, emailaddr...@[EMAIL PROTECTED]
wrote:
> > ..snip..
>
> >> However, it is fairly beside the point that I am looking for
> >> a universal equation that ignores all of this. Many people seem to
be
> >> saying the rest matters and yes of course it does - but it is still
> >> theoretically expressable in an equation with the factors that change
> >> as variables.
>
> > Universal equation. Here you go.
>
> >http://en.wikipedia.org/wiki/Heat_equation
>
>http://en.wikipedia.org/wiki/Newton%27s_law_of_cooling#Newton.27s_law...
>
> > Also check out "Introduction to Heat Transfer" by Incropera and
> > DeWitt.
>
> > The game is to keep the transformer wires at only a moderate
> > temperature higher than ambient, or you will melt the wiring
> > insulation.
>
> > Knock yourself out.
>
> > Michael
>
> These equations are only part of the overall solution. Transformers are
> complex physical entities with many materials having different thermal
> characteristics, and the temperature of any spot in the transformer
depends
> on the amount of power being applied, time, and the way in which heat is
> radiated, conducted, or convected away from the source of the heat. The
> winding insulation is rated at a certain temperature according to the
> insulation class, and may vary from about 105 C (Class A) to 180 C
(Class
> H).
>
> http://www.engineeringtoolbox.com/nema-insulation-cl*****-d_734.html
>
> That is for motors (and I think it applies also to transformers), but
here
> is information more specific to trannies, and allows for hot
spots:http://www.jeffersonelectric.com/cgi-bin/site.pl?3208&dwContent_conte...
>
> This shows a wider range of cl***** up to "S", which is 250 C. Now,
that's
> hot!http://www.pleo.com/ulsystem/eis_apply.htm
>
> This is a detailed do***ent with more formulas for the OP to use when he
> designs his
transformer:http://www.superiores***.com/uploadedFiles/News/White_Papers/emcwa-ne...
>
> Paul
Yep, my links were meant as a starting point. Boy is he going to have
fun if he takes heat transfer coefficients from natural convection
into account.
Did you know, Excel 2003 can solve Bessel functions? (useful for
solving partial differential equations in cylindrical coordinate
systems) Type BesselJ in the HELP toolbar, then follow the "How?"
link to install the Analysis ToolPak
Michael
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