Re: questions about tank capacitor (fwd)

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Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Thu, 31 May 2007 19:14:32 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: questions about tank capacitor (fwd)

Hi Dan,

A 15/30 NST is excellent choice for a first coil. Ramping up the input 
voltage is fine and does give you some control over the coil. Your tank 
cap value for a static gap of 0.008uF is what you want. But there's a 
little confusion:

The LTR value is identified as a percentage above the capacitance value 
that would cause the transformer to resonate at the line frequency of 50 
or 60 Hz operation. The LTR value is not affected because the resonant 
capacitance is not affected by the applied voltage. The transformer will 
reflect the load impedance back to the primary side as a function of the 
turns ratio squared. This occurs regardless of the applied voltage. One 
could always nitpick subtle changes which do occur due to non-linear 
currents, leakage, etc.., but for practical purposes, the resonant 
capacitance is unchanged.

I use a variac to ramp up my coils as well. Works great and with a 
variac you can boost that input voltage to about 140 Vac input which 
gives a slight boost to the output.

The mutligap is a good choice also. Makes sure you have plenty of 
airflow (important).

Take care,
Bart

Tesla list wrote:

>Original poster: List moderator <mod1@xxxxxxxxxx>
>
>---------- Forwarded message ----------
>Date: Thu, 31 May 2007 03:00:36 +0000
>From: d.grieves90@xxxxxxxxxxx
>To: tesla@xxxxxxxxxx
>Subject: questions about tank capacitor
>
>Hello everyone,
>
>I am building my first tesla coil and have many questions. I plan to power
>my coil with a 15 kV 30mA 450VA neon sign transformer with a variac to
>control the output, probably from 6 kV to 15 kV in steps of 1 kV or so. I
>am using a static gap made up of multiple gaps in series, allowing me
>change the total gap size to fit the voltage of each step. But I don't
>know what value my tank capacitor should be. I am planning to use the LTR
>value for the transformer at full voltage (0.008uF). At the lowest voltage
>settings however, this would be considerably less than the resonant value.
>Is this OK? Or should use the LTR value for the lowest voltage (6 kV), or
>maybe somewhere in between? I would greatly appreciate any suggestions or
>guidance, 
>thanks. Dan
>
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