Re: TC Secondary Terminal Design

To: tesla-at-pupman-dot-com
Subject: Re: TC Secondary Terminal Design
From: John Couture <COUTUREJH-at-worldnet.att-dot-net> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Tue, 24 Nov 1998 06:46:50 -0700
Approved: terryf-at-verinet-dot-com

At 02:21 PM 11/22/98 -0700, you wrote:
>Original Poster: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz> 
>
>Hi John,
>
>> Original Poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net> 
>> 
>> 
>>   All -
>> 
>>   Finding the proper size secondary terminal has now become easier when
>> using a new(?) equation that I have derived from several theoretical
>> equations. This is not a precise solution but does get you a ballpark
>figure.
>> 
>>  The sizing of the secondary terminal capacitance is part of the tuning
>> process and must satisfy the  Lp Cp = Ls Cs  equation. However, the size is
>> also determined by the input voltage and wattage. When the input voltage or
>> wattage is increased the secondary terminal capacitance should be
increased.
>> 
>>   The equation I derived to do this is as follows:
>> 
>>       Cs = 12.34 * cuberoot(KVp^2 * Cp)
>> 
>>      Cs in pf      Cp in uf
>> 
>>   Note that Cs in this equation is based on input voltage and  also on the
>> input wattage when  
>>   Cp = J/Vp^2  and  J = Input watts/ Breaks per second
>> 
>>   The equation is derived assuming the following:
>> 
>>   The secondary terminal is a sphere and
>> 
>>   Cs (pf) = sphere dia * 1.41    
>
>Under what conditions is that formula valid? Isolated sphere? 
>Remember that putting the terminal on a secondary makes the sum of 
>the individual components <> the sum of the two paired up.
>
>Malcolm

---------------------------------

  The formula is to get you in the ballpark. In the example shown if the
secondary coil self capacity is taken into account the sphere size would be
something less than the 17.8 inches. To my knowledge this is the only way to
relate the secondary sphere size to the input wattage of the TC at the
design stage.

  In the past coilers have only used the tuning conditions in selecting the
terminal. It is obvious that the secondary terminal should be increased when
the input wattage is increased other things being equal. The input voltage
cancels out if the TC is designed so that the primary capacitor is fully
charged at each break. 

  I used 65 Kv for the sphere breakout voltage. For some other voltage the
equation would be 

     Cs = 197.6 * cuberoot(KVp^2*Cp/Vb^2)

     Vb = sphere breakout voltage in KV  

  John C.

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