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>

 > >         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.

	Yep, these are exactly the parameters I was thinking about.  As for DC
current vs RMS you are correct of course.  In a resonant modulator of
the kind I'm familiar with (rectified and at least lightly filtered AC
feeding the charging choke) the waveform across the inductor is a half
sine wave, starting and ending at the negative and positive peaks [if
you use a "disconnect diode"].

 > >   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...

	Facts of life!

 > >  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.

	I'm sure of that.

 > 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.

	I found four NST's (one 9 kV 60 ma and three 12 kV 60 ma) lying in the
ice plant besides the northbound Harbor freeway onramp from Gave
Avenue.  I was riding with my brother in law in his pickup and just
happened to see one end of a transformer sticking up out of the plants
as he drove onto the freeway.  Got off at the next exit and went back
and picked them up, including some of the broken pieces of insulator
which were still on the road.  All worked and I am still using the two I
kept, and that was at least 25 years ago.  I'm sure these were lost
accidently by some idiot who just laid them on the bed of his truck and
didn't think.  Certainly no PCB's in them, just the usual tar.

 > 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.

	Still happens!  Just like people dumping their trash on the street or
draining the oil out of their crankcases onto the street.  A few years
back someone at the Northrop B-2 facility in Pico Rivera was trying to
organize an "adopt a highway" activity.  A couple of us in the rifle
club volunteered to camp out and shot the guilty parties but that wasn't
accepted.

	Your big resonant charging gadget sounds interesting.  More details
including expected results?  Someone here posted a lot of pictures of
his more or less professional TC which was truck mounted as I recall and
used resonant charging.  Awesome device and your proposed one seems to
be about the same size.

Ed