Re: Gapped DC Charging Reactor Performance

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>" <youngs-at-konnections-dot-net>

Mike and other DCers,

Today I hooked 5 (!) MOTS in series for a total of about 80.5 Henrys in my
DC resonant charger setup.  Total DC resistance was 365 ohms, which at 0.2
amp average, only wastes about 73 watts plus a little more for Eddy current
losses as the field builds up and collapses.  In other words, insignificant
compared with gap losses.

With the large reactor, I could reduce the BPS to 100 and still run full
power without power arcing.  At 50 BPS, however, as I cranked up the power,
the RSG would suddenly draw out tremendous power arcs, probably 6 inches
long total!  I am amazed that the power supply and series connected de-Qing
oven diodes can take that punishment!  For me, 100 BPS is an acceptable
lower limit as the TC performance is rather wimpy at slower rates.

I didn't notice any decrease in performance at BPS up to 500.  I can still
get streamers over 54 inches.  500 BPS is 2 milliseconds between bangs.
Using V=Ldi/dt and solving for dt, I get about 1.4 ms for V=8,400 volts and
I=150 ma (at 400 BPS).  Seems like one would have to have break rates higher
than 1/1.4 ms = 714 BPS before the tank cap wouldn't fully charge.  I am
chicken to run my RSG that fast.

Hmmm, at 300 BPS, dt= 1.1 ms for 9.3 KV and 132 ma, and at 500 BPS, dt is
about 2 ms (7.4 KV at 192 ma), so there seem to be too many variables to
draw specific conclusions.

So, who is going to be the first to build a single 100 Henry DC charging
reactor?

--Steve
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, December 16, 2001 8:20 PM
Subject: Re: Gapped DC Charging Reactor Performance


> Original poster: "Mike Nolley by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<nolleym-at-willamette.edu>
>
> > So I think one should select 2 MOTs with high inductance (they seem to
range
> > from 10 to 20ish Henry - use the 20+ Henry ones), gap them both, and run
> > them in series.  Next best is to use 3 or 4 ungapped MOTs in series.
For
> > extra credit, construct your own 50 Henry gapped DC charging reactor!
The
> > alternative is to always use BPSs of more than 450 with small diameter
gap
> > elements on a large diameter RSG (to minimize dwell times) and just use
one
> > MOT.
> >
> > Comments and your experiences welcomed please!
>
>     Great results!   It might be interesting to see how far one could push
> the inductance before the
> gap firing voltage decreased. (the larger the inductance, the longer it
> takes to charge--if the
> inductance is too large it won't charge to maximum voltage) It might be
> useful to find an ideal
> inductance-per-breakrate.
>     I think using the un-gapped Mot is probably the best solution for
those
> who aren't constrained
> space-wise, since the advantage may not be all that great, considering the
> drop in inductance.
>     I'm planning on building my own Mot power supply in the next month or
> so, and I'll keep you all
> updated.  Thanks for your work Steve!
>                 --Mike
>
>
>