Re: Charging inductors for resonant charging

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

Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net> 

Ed, Jim and all,

Here's an idea I was kicking around with Ed Wingate a while back. You could 
simply use another distribution transformer and ballast as a HV charging 
inductor. Use the HV winding in series as the charging inductor. Connect 
the low voltage side of the DT to high current ballast (welder or 
adjustable high current inductive ballast). The DT will multiply the LV 
side ballast inductance by its turns ratio squared, easily making the HV 
side look like a large, adjustable, HV inductor. And a properly sized DT 
already has the necessary BIL and current rating required.

By selecting the proper distribution transformer and ballast, you should be 
able to get almost infinite flexibility with without the need to resort to 
a custom HV choke.

Best regards,

-- Bert --
-- 
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Tesla list wrote:

>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
>
>.