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



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. > > > > > > > >