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

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Jim,
         Deciding whether to put the choke on the primary or
secondary side of the transformer can be summed up with a simple
comparison:

Pros for primary side choke (often referred to as the "ballast"):
- high BIL-rated transformer has to withstand all the extra voltage
burden which it is suited to do; the choke is transformed to the
secondary side where it resonates with the primary cap
- choke can be a small value but has to withstand high currents

Pros for secondary side placement:
- choke has to operate at high voltages and be insulated to do so
while removing the voltage burden from the transformer
- current is lower but inductance has to be high

There are probably other factors I've forgotten to mention.

Malcolm


On 6 May 2005, at 12:16, Tesla list wrote:

> 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. >  > >  > > > > >
>
>
>