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

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mark Dunn" <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" <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.