Re: Air Gap MOT Reactor

["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>

Gregory & other interested bystanders,

Answers below:
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, December 07, 2001 11:41 AM
Subject: Re: Air Gap MOT Reactor


> Original poster: "G by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<bog-at-cinci.rr-dot-com>
>
> >By the way, some worry about MOTs not being able to withstand high
voltages
> >across the secondary.  I think they are good for 10 KV or so.  They have
to
> >be insulated well enough to not break down when power turns off at the
peak
> >AC voltage and the magnetic field rapidly collapses, generating more than
> >the usual 2 KV  steady state output.  I have run 9 to 10 KV DC into a MOT
> >charging reactor with no signs of breakdown.  Remember, the charging
reactor
> >nearly doubles the DC supply voltage so one doesn't need more than about
10
> >KV DC to charge the tank cap to nearly 20 KV.
> >
> >I would be interested in hearing of others trying gapped MOTs as cheap
> >charging reactors.
> >
> >--Steve
>
> One point on the breakdown voltage- unless the core is grounded, the
> only voltage I think the insulation would have to withstand is the
> tank RF trying to jump across the inductance. The de-Qing diode
> should help with this. At DC, I don't think the windings would have
> any voltage to the core at all.
>
ANSWER:  Not so!  Where do you think the voltage to double the supply
voltage comes from?  It comes from the reactor which will have about the
same voltage across it as your DC supply.  The reactor voltage decreases
from Vsupply to 0 as the tank cap voltage increases from 0 to nearly
2Vsupply for each bang.

><snip>.
> One question- Richie shows the DC charging circuit connected across
> the tank cap, not the spark gap. Will this configuration reduce the
> tendency to power arc? With the charging choke and diode blocking RF,
> do we still need to be concerned about the current oscillations
> Terry's NST research found? It would be nice to set the charging
> circuit inductance with the choke alone, without having to take into
> account the primary coil. The primary inductance may adversely effect
> the inductive-kick of the choke (not sure about that one yet!)
>
ANSWER:  No - same power arc can occur in either configuration.  The only
difference is that in Richie's circuit you have another 50 feet or so of
copper tubing in series with the gap and the DC supply.  The inductance of
the primary  is miniscule compared to the reactor and will make no noticible
difference.  (My charging reactor is over 10 Henry, my primary is 27
microHenry!)   But I like the gap across the supply/MOT as I think it will
bypass more of the RF coming from the tank circuit.

> good luck!
> Gregory

I might note that I increased my MMC from 19 to 26 nF, retuned, and
discovered the tendency to power arc at lower BPS is reduced!  Not exactly
sure why yet.

One of these days I will reconfigure my charging reactor supply to run into
my SPDT RSG so it will charge the tank cap in position one and discharge the
tank cap through the primary in position two.  This disconnects the power
supply completely from the tank circuit when it fires, and will avoid all
power arcing.  But then I will have twice the gap losses.  I will report
results when I get time to try this.

--Steve