Re: Charging inductors for resonant charging

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

Original poster: Ed Phillips <evp-at-pacbell-dot-net> 

Tesla list wrote:
 >
 > Original poster: Jim Lux <jimlux-at-earthlink-dot-net>
 >
 > At 08:01 AM 1/29/2004 -0700, you wrote:
 > >Original poster: Ed Phillips <evp-at-pacbell-dot-net>
 > >Tesla list wrote:
 > > >
 > > > Original poster: Jim Lux <jimlux-at-earthlink-dot-net>
 > > >
 > > > What sort of sources are there for a 5-15 Henry charging inductor for a
 > > > resonant charging circuit? RMS current would be in the 1-2 Amp range.
 > > >
 > > > Is this a "wind it on a MOT core" kind of thing?
 > >
 > >         I'm no a magnetics designer but that sounds like a HUGE device 
to me!
 > >If the charging frequency was 120 Hz the reactance of the 5 henry choke
 > >would be about 3770 ohms and the voltage across it at 1 amp would then
 > >be 3770 volts.  If it is to pass 1 amp the wire size would probably have
 > >to be around #22 even for intermittent operation, and the resulting wire
 > >area would require a large core.  Real designers step forward?
 >
 > So then, what ARE people using for charging chokes in resonant charging
 > systems..

	Large inductors; maybe someone here can help.  I have one or two
charging chokes used for a 250 watt average power radar modulator and
they're about as big as an MOT.  I don't remember the ratings but have
saved them for many years with the idea of using them in a resonant
charging circuit for a "DC TC".  I have a 7500 volt 60 Hz power
transformer out of an old Navy radar and intended to rectify it and use
resonant charging along with an RSG.  Like many other projects it has
yet to get off the ground.

	Maybe I've misinterpreted what you wrote.  I'm used to thinking in
terms of average DC current, peak operating voltage, and frequency.  I
just dug out "Volume 5" (Glascoe and Lebacqz) and in Figure 9-13, page
375, they show samples of various DC charging inductors.  The biggest
one in the picture is rated at 0.4 amps, 17 kV peak, and has an
inductance of 19 henries; it weighs 71-1/2 pounds and is potted in a can
which looks like about a 7" cube.  You seem to want something over twice
as big.  There's a whole chapter of the book devoted to "charging
circuits for line-type pulsers" of which I'd say a TC is a degenerate
case.  There is some information on "THE DESIGN OF D-C CHARGING
REACTORS".  Almost the first sentence reads "Reactor design is usually
based on experience.  However, in the absence of suitable previous
experiende the design process can be started mathematically."  Design
equations and discussion follow, which don't look too horrid.  About
four pages of stuff which I could copy and send you if you're
interested.  I notice that the magnetic units are ampere turns/in (not
so bad) and flux is expressed in "lines" (lines/square inch).  The work
described was started about 1942, the same year I started in engineering
school, and apparently the authors had studied the same system of units
as some of my instructors.  We had so many different systems of units
(english, cgs, MKS, MKS rationalized, etc.) thrown at us that I've been
perpetually confused.

	I suspect your reactor could be wound on the core of a transformer
weighing of the order of 100 pounds or so, and if memory serves me right
small pole pigs fit into that class.  Someone who owns some might
correct me.  In the "good old days", here in the Los Angeles are it was
possible to go to the Edison Company salvage yard in Alhambra and pick
up small (unpotted) pole pigs for free.  2200 volt to 110 volt units
were good for plate transformers for ham transmitters and I suspect
there are some of them still around.

Ed