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

["Tesla list" <tesla@xxxxxxxxxx>]

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.
>
>