Re: Air-core power transfomers

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "rob by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rob-at-pythonemproject-dot-com>

Tesla list wrote:
> 
> Original poster: "Marry Krutsch by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <u236-at-earthlink-dot-net>
> 
> Hi all.
> 
>         I've been interested in those solid state MOTs ever since someone
here
> mentioned them.  Since discarded microwaves are scarce around here
> (that, or someone is beating me to them ;-)), I wanted to make one
> myself to power a DC coil, and to feed smoother power to magnetrons.
> 
>         Anyway, I've got plenty of wire, but no ferrite for the core.  Can I
> make an air core "MOT"?  What are the potential problems with this?
> Should I let the inductive reactance of the primary limit the current,
> or should external limiting be used?  Does air "saturate" the way iron
> does?  I'm thinking that operation at 50 kHz or so is good.  And now the
> stupid question:  Does the primary (drive coil) need to be wrapped
> around the secondary (driven coil)?  I thought that coupling would be
> better in this case, but really don't know.  Thanks for any help.
> 
> Winston

If you use high voltage FETS in a half bridge, you may be able to drive
the coil directly from the FETS through a blocking cap.  I haven't tried
this, but its on my list of things to do.  I don't fool around building
such power supplies.  I just get a good >300W switcher, and cut the
board in half.  Then feed my own signal into the FET gate-source
isolation transformers.  Rob.


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