Re: Charging inductors for resonant charging

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

Original poster: Jim Lux <jimlux-at-earthlink-dot-net> 

At 12:02 PM 1/30/2004 -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?
> >\re 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.

Frequency meaning the PRF?  Average current/RMS current.. heating is going 
to be RMS current related, I should think,and would determine the size of 
the wire (and cooling). Average current would be how much power we're 
putting through the system.  Voltage: it would have to stand off the usual 
tank circuit voltage, so say, 15-20kV or thereabouts. Average 
current*voltage gives the power (10-20kW in this case) , divided by the prf 
(400-500 bangs/sec in this case), gives the energy that has to be stored in 
the cap at the end of the "charging interval" -> 20-40 Joules.  Some comes 
from the bulk supply, some comes from the energy in the choke (assuming 
we're doing real resonant charging, as opposed to inductive disconnect).. 
Say, 20 Joules.  L = 1/2*LI^2... I = 2 so L=10 or thereabouts.





>   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.

That's kind of what I was afraid of...



>         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.

Hah.. I'll bet no utility in California has disposed of anything like this 
in an uncontrolled manner for decades.  Porcelain insulators, sure. ACSR 
cable, sure. Vacuum switches, sure.  Something with "oil" in it, not a 
chance.. They have a deal with a hazmat disposal company who accepts the 
"cradle to grave" responsibility.  They live in paranoid fear that 
somewhere down the line, someone will find a leaking widget in a vacant 
lot, see the SCE or DWP tag on it, and go attack everyone who might have 
had custody at some point.  Such being the laws about hazmat.. to prevent 
companies from disclaiming responsibility by transferring all their nasty 
stuff to someone else, who then lets it fall off the back of a truck somewhere.

There was a story about a well known hazmat hauler in Southern California 
who would pick up liquid waste and truck it to the Casmalia disposal site 
(near Santa Barbara.. 100 miles or so from Los Angeles).  Oddly, the trucks 
were very lightly loaded when they arrived at the disposal site, so they 
didn't have to spend too much on the disposal fee (which is by weight of 
the material disposed of), and the company was able to offer very 
competitive disposal rates to their clients.  Gosh.. it turns out that 
those careless drivers would forget to tighten the cap on the drain pipe 
and make sure the valves were closed. (after an incident where a driver had 
some mechanical failure or stopped to eat lunch or something, and someone 
noticed that there was this stinky corrosive puddle with fumes visible 
forming under the truck and called the Cal Highway Patrol).  Such incidents 
(hopefully rare) are what motivates seemingly vindictive disposal rules and 
tons of paperwork.