Re: RE: weird resonance with HV cap

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx>

Chris,

You can't get a good measurement of the primary resonant frequency unless
you disconnect your secondary top load so the secondary frequency is much
removed from the primary frequency.  Otherwise, you end up measuring the
secondary frequency coupled through the primary.

I have found that it is best to measure the secondary resonant frequency
with topload and primary open circuited.  Then disconnect the secondary
topload, connect your primary cap across the primary, and tune the primary
to a frequency a few percent lower than the secondary.

Another method which I prefer is to attach a length of wire to the topload
to simulate the expected leader.  For example, if you expect to produce 4
foot leaders, connect a 4 foot wire to your topload and suspend the free end
horizontally with some string.  Measure the secondary Fres, then tune the
Primary Fres to the same frequency.

--Steve Y.

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, March 16, 2006 5:19 PM
Subject: Re: RE: weird resonance with HV cap


> Original poster: Chris Estes <estescc@xxxxxxxxxxxx>
>
>
>
>
> Tesla list wrote:
>
>
>  >Original poster: "Leigh Copp" <Leigh.Copp@xxxxxxxxxxx>
>  >
>  >Chris,
>  >
>  >As you probably know, neither your function generator, nor your
>  >capacitance meter are really producing enough current to simulate actual
>  >operating conditions. The difference between the theoretical response
>  >based on the cap meter reading and the measured fo may have more to do
>  >with the cap meter reading. The fact that the cap meter typically looks
>  >at a very limited range of frequency or dv/dt (depends on the kind of
>  >meter) to make its measurement, may skew the reading significantly on a
>  >capacitor with more dielectric. Your function generator probably has
>  >much more output current than the cap meter, and is going to be able to
>  >more completely polarize the dielectric in your homemade cap.
>  >
>  >I'm a bit confused - you said you had the scope -and- the generator on
>  >the secondary? Did you mean the gen was on the primary, and the scope on
>  >the secondary?
>  >
>  >Leigh
>
> Well, first I just measured the secondary resonance. I drove the bottom
>   of the secondary with one lead of the gen and grounded the other and
> then probed the topload with the scope probe and I had the gen and
> scope and ground wires as far away from the topload as possible to make
> the capacitance as close to what the actual capacitance between the
> topload and earth really is. Now I'm driving the primary with the gen
> and viewing the primary on ch. 1 and probing the secondary on ch. 2. If
> both circuits are matched I should see the amplitude of the primary
> rise and then see a big rise in the signal from the topload. I'm going
> to try some saltwater caps with some hdpe buckets I just got. I really
> need to get this thing done so I won't have any excuse for not working
> on my thesis. :)
>
>
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