Re: design presentation, and 1 question
Subject: Re: design presentation, and 1 question
From: Terry Fritz <terryf-at-verinet-dot-com>
Date: Wed, 02 Dec 1998 07:21:12 -0700
Hi DR.RESONANCE and All,
I use a 60mA transformer with a 17.05nF cap. It works great and charges
the cap just fine. In fact, I really should go to around 19.5nF to get the
best charging but my cap value will not adjust that high (thus my new cap
project). 19.5nF will charge the cap to around 20 kV from my 15kV/60mA
neon with the system starting from zero volts after the last gap firing.
If I use a 10nF cap, my output power drops dramatically. Probably by
about 1/2 since the stored energy in the cap is reduced by that ratio too.
With a 10nF cap I could use resonant charging to get to a higher voltage
and higher energy but I would need 30kV peek voltage to get to the same
energy level. This would substantially exceed the ratings of the
transformer and challenge the primary caps. Also, the safety gaps would
have to be set to say 35 to 40kV in that case. So if the gap failed to
fire, the transformer could see very high over voltage. I don't think the
added current is of great concern to the transformer in this situation but
it does add to heating...
I have been recommending using as high of cap value as possible that still
allows the capacitor voltage to reach the transformer's rated peak voltage.
I get great energy and the system operates within rated voltages. Since
the load is great enough to prevent over-charging, the system operates very
safely. In limited testing and calculation, this has worked out to about
twice what the classic load matching equation suggests. Unfortunately,
computer models that have the complete primary charging system (especially
the transformer) modeled are needed to calculate this accurately or you
need a high voltage (the regular high resistance kind) to check the voltage
at the caps. I have not done enough testing to be sure that the "twice
what the classic equation rule" works for all neon transformer types.
I use a 120 BPS rotary sync gap in this system. The gap fires about 5.5
mS after the transformer input AC peak due to the delay caused by the cap
charging. The rotor is set to delay the firing ~1/6 of a rotation behind
the AC line (1800 RPM). Perhaps a smaller cap could fire faster and
deliver the same power with some good safety margins?
At 11:17 AM 12/1/98 -0700, you wrote:
>The 50 ma of drive current will not be enough to charge your cap correctly.
> You will either need to go down to a .01 MFD cap or increase your drive
>current to around 120 ma to properly drive the .02 MFD cap. A .01 MFD cap
>will work but will require more primary turns to set resonance properly.