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Re: SS MOT's ----> possible mod's for TC Power

Original poster: "Justin Hays by way of Terry Fritz <twftesla-at-qwest-dot-net>" <pyrotrons2000-at-yahoo-dot-com>

Hi All,

(the following is a snip from Alex)

> 	I just read an aritcle in the current 
> edition of new scientist that samusung are 
> planning to make toaster sized microwave 
> ovens using switch mode power supplies - 
> these are apperently 95% lighter and 75% 
> smaller than a standard MOT. It'll be 
> pretty cool when they start showing in 
> scrap yards, imagine - 2kw coil that only 
> weighs a few Kg's.

Panasonic has already done it to some degree...but not to the spec's
you quote I don't think. To me it seems unreasonable that you could
stuff 600W at 2.5kV into a package 75% smaller than a 4" x 4" x 4"
MOT. But SMPS technology is getting AWESOME nowadays, so maybe so.
Power density keeps going up and up...and weight/size is going down
and down. I think eventually, like everything else, there will be a
limit but I don't see it stopping soon. It all depends on the quality
of the semiconductor used...but I digress, so anyway.

These things are NEAT, especially since the output transformer of one
could be modified to give more output voltage. I'm thinking add a few
hundred more secondary turns and see what happens...there will be
more reflected voltage stress on the power switches (IGBT's) but I
bet it could be done. Perhaps an IGBT with a higher voltage rating
could be swapped out with the original one. 

If this could be done, it just replaced every one of the heavy,
tar-potted NST's in my shop. Of course, this means going DC and a big
rectifier stack, but I'll take it.

I found one of Panasonic's "inverter technology" microwaves in the
local junkyard. I pulled it out of the trash heap by the cord --- and
nearly threw it a hundred yards expecting there to be a 25lb. MOT in

Aron (partner in crime) and I tore it apart and tested the really
cool looking switcher. There were two IGBT's, one big, one a little
smaller. The big IGBT was fried, so we took the small IGBT out as
well as the output transformer.

We used Aron's signal generator and gave it 50kHz....while turning up
the input voltage with a variac. 

The output was MEAN. It looked like a MOT arc, except no 60Hz. It was
a nice smooth floating thing....and would melt/burn anything. We
eventually cooked the IGBT, so we salvaged the nice wire from the
transformer and of course, the giant ferrite core.

I just put up a picture of the arc, if interested go to:


At the very top, the first link underneath the "Featured Items"

By the way, something fun to do is pick up all the microwaves at
Wal-Mart, every one of them one-by-one, and try to find one that uses
the new inverter design. It's not hard, there is a big difference in
weight (size is the same, as they still must allow for big meals).

Take care,

Justin Hays
Email: justin-at-hvguy-dot-com
Website: www.hvguy-dot-com

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