RE: DC coil without the voltage doubler resoance charge inductor?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>


Jim:

I don't completely understand your question...
But in my case I feed the FW rectifier ~7KV and pull ~200 mA from my
MOT's and have ~10 KV on the DC side of FW and filter caps.  This gives
me a 1.5/2.0 KW system.  Is your expectation to go to much higher
KW(which obviously you can with your pig, but you need a big coil to do
that)?  As I told Paul, I would use MOT secodaries in series for the
charging reactor to get the unit working, then build an appropriate
charging reactor for long term use.  My experience with my voltage and
current is the MOT secondary insulation fails in charging reactor
service after some hours of operation.  Note Steve has different
results.  I am afraid this does not answer your question, because I
think you might really be asking about the design of air chokes to use
in place of the charging reactor on both DC legs.  In any event, you may
find this info useful or not.

Best of Luck.
Mark


Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

HI ALL, I am having a hard time understanding how Mot's with out a lot
of series paralleling to contain the inductance on target can withstand
the torture of the high current demand and 30KV voltage doubling + from
my pole pig power. It seems to me that a similar choke would need to be
constructed consistent to a pig sans LV and even better insulated,
constructed, and rated HV windings. This Steve does not take into
consideration your spdt gap but rather the Burnett configuration. I plan
to try both. Am I missing something here? Smoking the choke seems like a
very bad outcome...and a run away condition. Poof. Any other ideas on
limiting the charge from the filter caps to the tank?

Thanks for the educating posts.
Jim Mora, Resistor naysayer
Ojai,ca

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Thursday, May 05, 2005 8:47 PM
To: tesla@xxxxxxxxxx
Subject: Re: DC coil without the voltage doubler resoance charge
inductor?

Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx>

Paul,

I'm not Mark, but I believe the inductance of your NST will be so high
that you will not be able to fully charge your primary cap except at
very low break rates.  I have used 4 MOT secondaries in series as a
charging reactor with no problems with breakdown.  The MOTs need to be
mounted on insulators and separated from each other, of course.

--Steve Y.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, May 05, 2005 5:31 PM
Subject: Re: DC coil without the voltage doubler resoance charge
inductor?


  > Original poster: "Paul B. Brodie" <pbbrodie@xxxxxxxxxxxxx>
  >
  > Mark,
  > I have been considering duplicating your DC resonant charging
configuration
  > and have most of the parts required minus the charging reactor. I
was
  > considering using the secondary of a 15kV NST for this but after
reading
  > about your experience with the MOT secondary burning out, I have
second
  > thoughts. I do realize that the NST secondary is designed for 15kV
vs. the
  > 2000kV of a MOT. What is your opinion about this idea? Thanks.
  > Paul
  > PS Your previous emails and your web site have been extremely
helpful.
  > Thanks again.
  >
  > ----- Original Message -----
  > From: "Tesla list" <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
  > To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
  > Sent: Thursday, May 05, 2005 1:21 PM
  > Subject: RE: DC coil without the voltage doubler resoance charge
inductor?
  >
  >  > Original poster: "Mark Dunn"
<<mailto:mdunn@xxxxxxxxxxxx>mdunn@xxxxxxxxxxxx>
  >  >
  >  >
  >  > Jim:
  >  >
  >  > I use a DC system with great success.  I have a homemade 31 H
charging
  >  > reactor built on a gapped U-100 Ferrite core in series with the
d-q
  >  > diode.  Orignally, I used two MOT secondaries in series(15 H ea)
but
  >  > eventually the insulation breaks down on the secondary wire and
arcs
  >  > over in the secondary causing the inductance to drop.
  >  >
  >  > I used 1N5408 diodes in series to create the d-q and F-W
rectifier(4
  >  > groups obviously).  Each diode is parallelel with a 1.2 megOhm
resistor
  >  > and 1 nF ceramic disk snubber cap(I built these boards a couple
years
  >  > ago so I'd have to dig out the math if you want to know how I
arrived at
  >  > those values-I know the resistor was picked because I could get a
bag of
  >  > 200 for $5). My rectifier/power supply design produces + and - DC
legs
  >  > and I have a series of caps to give me 1.5 uF of filtering(reduce
  >  > ripple) between each DC leg and ground.
  >  > The filter caps are a series of cheap 450volt electrolytics.
These are
  >  > also paralleled by 1.2 mOhm resistors for bleed down.
  >  >
  >  > I think you need the charging reactor(CR) so that the rectifier
does not
  >  > see a dead short when the spark gap is firing.  The CR protects
the
  >  > rectifier because it makes current lag voltage, but that is
obvious.
  >  > Secondly, it protects the rectifier from the RF as you pointed
out, but
  >  > you have a plan to stop that problem(I think - I have no input
for you
  >  > on you RF choke design concept).  The additional feature of the
CR to
  >  > double voltage is not an issue for you.  By the way, I have the
CR on
  >  > the + DC leg.  I always have wondered what protects the -DC leg.
  >  > Assumed it was because there was no current flow, but RF is
always
  >  > "looking" for ground.
  >  >
  >  > Please note I am operating at lower voltages than you.  I am
using a
  >  > series of MOT's to produce (2) 3500 VAC legs 180 deg out of
phase(net
  >  > 7000 VAC.  After the rectifier I have (2) DC legs, one at +5000
VDC and
  >  > the other at -5000 VDC.  Thus, my Vrrm is only 11,000 volts due
to the
  >  > center tapped type design.  Each of my diode strings is thus only
(12)
  >  > diodes. I did use a (20) diode string for the d-q.
  >  >
  >  > Mark
  >  >
  >  >
  >  >
  >  > Original poster: "Jim Mora"
<<mailto:jmora@xxxxxxxxxxx>jmora@xxxxxxxxxxx>
  >  >
  >  >
  >  > Hello all,
  >  > DC Coil: I have acquired all the parts and am in various
construction
  >  > phases of the 11" linear variable rotor 0-500bps spark gap,
safety
  >  > resister banks (tiger strip network) 3 min bleed down from a 4Uf
20KV
  >  > Maxwell filter/ smoothing cap. 100k 150 watt safety Bang
fiberglass
  >  > stick. I will short and ground this before I go down stream!
  >  >
  >  > After pounding my head I see no advantage to a HV charge inductor
as I
  >  > am able to deliver 20365v @ 8k watts easily with my pig 14400
5kva
  >  > (harder to come by in UK I guess) (in a 10KVA tank)Ultimately, I
would
  >  > like to charge ~ 80nf with up to X^limit? bps and in the 8kva
ball park.
  >  >
  >  > The charge inductor seems to be a source of failure for many who
have
  >  > gone down this road? I am thinking of retaining my welder and
ballasting
  >  > the LV side of the pig.
  >  >
  >  > **A few design questions?*** The FW Bridge will be made from  4
stacks
  >  > of(6)studded 7.5KV each 4.5a diodes part # hvca hdb7.5 9928
(Altronics).
  >  > These should all have a snubber across them yes? Suggested value,
type ?
  >  >
  >  > I have a (100) 1N5408 1000v 3or 4 amp doides I was thinking of
  >  > paralleling 2 and series 40 pairs of these as d-Q is a one nano
snubber
  >  > across each pair prudent?
  >  >
  >  > Lastly the RF coming back from the tank to reek havoc and pillage
the
  >  > rectifiers. Searching the achieves, "a simple 1"x 6" open air
coil of
  >  > house wire should act as block" or HV wire wound on a Large
torrid such
  >  > as a TV deflection coil?" Are we buying this? I would appreciate
some
  >  > guidance folks.
  >  >
  >  > Thanks Much
  >  > Jim Mora
  >  > Ojai, Ca.
  >  >
  >  >
  >
  >
  >
  >