OLTC-Inductors

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi All,

Well, I guess I should have known I was in trouble when I got zero response
to this one :-))  

I dumpster dived for some inductor cores today and found and made up this
fancy 75mH choke:

http://hot-streamer-dot-com/temp/OLTC8150011.jpg

but it saturated in testing:

http://hot-streamer-dot-com/temp/OLTC8-15-02.gif

Oh oh..  That amps per turn stuff...  I ain't no golly darn transformer
design genius...

I played with some transformers and such but saturation is a BIG issue!  I
took an old core from a variac and sliced it with a little finger nail
file...  Hahaha!!  I used a cobalt alloy M42 hacksaw for cutting mil grade
6-4 titanium :o))  Cut it like butter...

http://hot-streamer-dot-com/temp/OLTC8150009.jpg

It solved the saturation and gave ideal inductor responses:

http://hot-streamer-dot-com/temp/OLTC8-15-01.gif

But it only measured 47mH....

So, to make a long day's story short, the resonant charging inductor is a
big issue!!...  I think it has to work at 120Hz (helps a LOT! as opposed to
60Hz...)  Saturation is a killer.  Probably going to need some "big iron"
cores here!  Not to bad really, but I thought this would be a trivial
part...  I don't think an air core inductor would work given the low (5
ohms) resistance needed.

The Devil is in the details...

Cheers,

	Terry



>Hi All,
>
>I have been working on the inductors for the OLTC tonight.  Actually, just 
>thinking about them...  The "specs" are:
>
>1.  Easy to make and reproducible by your average coiler (or easy to just 
>buy out right).
>
>2.  Light weight since this coil is "hoot'n and toot'n" about no heavy "big 
>iron" stuff in it.
>
>3.  Can reasonably handle the voltages and currents shown (note that the 
>current is 100X in the pic):
>
>http://hot-streamer-dot-com/temp/OLTC8-14-03.gif
>
>About 5.5 amps peak and 650 volts peak.
>
>3.  The FT looks like this:
>
>http://hot-streamer-dot-com/temp/OLTC8-14-04.gif
>
>Looks like all 100Hz to 1kz stuff.
>
>4.  There are two inductors at 75mH each.  They could probably be on the 
>same core in some common mode if that would make things easier.
>
>Here is the system schematic (Lb1, Lb2):
>
>http://hot-streamer-dot-com/temp/OLTC8-14-02.gif
>
>5.  Not too expensive, but realizing this is probably like a $500 class
coil...
>
>If anyone has any ideas here they are very welcome :-))  Either on list or 
>direct to:
>
>terrellf-at-qwest-dot-net
>
>I guess it could be one 150mH inductor, but the filtering and "balance" 
>seems more natural with two inductors.
>
>Cheers,
>
>	Terry
>