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Primary Qs


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.  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.  
        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.
Regards,
Mark S. Rzeszotarski, Ph.D.