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Primary Qs


From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Tuesday, September 23, 1997 2:32 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Primary Qs

Hi Mark,
 
> From:   Mark S. Rzeszotarski, Ph.D.[SMTP:msr7-at-po.cwru.edu]
> Sent:   Tuesday, September 23, 1997 2:29 AM
> To:     Tesla List
> Subject:    Re: Primary Qs
> 
> Hello All,
> Malcolm Watts stated:
> >        While my neons were alive, I tested two resonators in two 
> >different types of primary (helix and saucer). The resonators differed
> >mostly in that one resonated at 420kHz and the other at 280kHz with 
> >identical toploads. Cselfs were much the same. I used a 12kV 60mA 
> >paralleled with a 12kV 30mA. I got far better results in both types
> >of primary with the lower frequency resonator. The only reason I can 
> >attribute that to is the higher primary Q I got with lower frequency 
> >running. The primary cap was also identical and single shot 
> >measurements showed output voltage to be roughly the same. Both 
> >resonators are wound with large enough wire to discount secondary 
> >losses from the mix. I was getting solid three feet strikes with a 
> >25nF CP primary cap from the low frequency resonator but only about 
> >2-1/2 feet from the higher frequency one.
> 
>         Assuming the coefficient of coupling was identical for the two coil
> systems, the most likely explanation is as you say primary coil losses.  The
> surge impedance for the low frequency coil is about 23 ohms, and 15 ohms for
> the high frequency case.  If your gap losses are significant (estimate 6-12
> ohms for a dual static gap), most of the difference can be accounted for
> simply by the higher surge impedance of the low frequency coil, which
> reduces gap losses.

Exactly my reasoning.

>  Do you have enough primary inductance to operate with
> both your 25 nF CP caps in series, thereby increasing Zsurge a bit?  This
> would require about 25.9 uH for the low frequency unit and 11.5 uH for the
> high frequency coil.  This would raise Zsurge to 45 and 30 ohms
> respectively, which is where I prefer to operate these days.  

Me too. Unfortunately I don't have the primary voltage to make up for 
the loss in capacitance.

>         Sorry to learn of the death of your NST.  I have killed several.
> Thanks to Glascoe, I now understand a bit more about resonant charging and
> its effect on things in its path.  I am building a new 10 kV D.C. supply to
> do some single shot experiments and have wound some 14.5 mH chokes for each
> side of the supply to try to keep kickback out.  We shall see how well it
> works in the next few nights.

I am delighted it happened because I learnt a hell of a lot (and I 
must apologize here to the big boys who undoubtably know all this).
It seems there are a bunch of things conspiring against static gaps. 
Opening them up to use resonant charging increases their losses and 
also subjects the transformer to much higher voltages at 2Fmains. 
That second one is obviated by using an external charging choke.
    The other problem with the wide gap though is that it tends to go 
out earlier in the piece. As I found, that is kickback generation 
material. I'm in the process of learning to convert induction motors 
for sync gaps which, based on much evidence from Skip and John would 
seem to be the ideal choice of gap as long as the dwell time is not 
excessively short.
    I've never had a problem ever with single shot testing from a 
HVDC supply and it is the most potent weapon in my experimental 
armoury.

Regards,
Malcolm