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Re: MOT prices



Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

> The sticker rating is usually the best clue you can have.  You can
probably
> draw about 1.5 times the sticker rating for short times.  The rest of the
> oven stuff (light, timer, etc.) draw an insignificant amount of power.
> Weight vs VA is not a very good measure.  About all you can rely on is
that
> bigger, heavier MOTs likely can handle more power.

And of course, you COULD actually measure the power handling capability by
measuring temperature rise with a known load.  All that copper wire in the
windings makes a nice thermometer. Measure resistance cold.  Put a load on
for a minute or so, disconnect and measure resistance again, repeat a few
times until it reaches equilibrium.  Do a bit of calculating to determine
delta T, thermal mass, and time constant.

Core cross section is probably as good a measure as any, by the way...Easy
to measure, and you can develop a cross section/rated power curve by
studying some of the online microwave oven transformer catalogs. Yes, folks,
you CAN just do a google search for microwave oven transformer, and you'll
get a few hits for the companies in Korea and Taiwan that make the darn
things...the catalog pages might be in Chinese or Korean, but the numbers
are readable, and you can figure out what's what...

I suspect that there are relatively few significantly different models,
since there aren't all that many magnetron models around (at least that
differ in ways other than the mounting brackets, etc.). There's only so many
ways to make a 2.45GHz magnetron, since the cavity dimensions are determined
by the frequency, and everyone buys the same magnetic material, etc.