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Re: TC Criticall Coupling (was Overcoupling?)


  Malcolm -

  What was the "K" coupling at 90% efficiency? Did you make any other
coupling vs efficiency measurements?

  Are you saying that equal amounts of energy are lost in the TC rimary and
secondary circuits at critical coupling (50% eff)? Please explain.

  John Couture

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

At 01:28 AM 5/7/99 -0600, you wrote:
>Original Poster: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz> 
>
>Hi all,
>        IMHO, the notion of critical coupling should forever be 
>thrown away in the context of Tesla coils. It is obvious if one 
>examines the waveforms on the scope that a TC can do *far* better 
>than losing equal amounts of energy in the primary and secondary 
>circuit. I have personally measured a transfer efficiency approaching 
>90% in a small coil. You can see the primary ring down to zero while 
>the secondary rings up and if ideal quench is effected, the energy 
>is contained in the secondary circuit or lost in impedances attached 
>to it, hopefully an output discharge. 
>
>> Original Poster: "John H. Couture" <COUTUREJH-at-worldnet.att-dot-net> 
>> 
>> 
>>   To All -
>> 
>>   Has anyone designed a Tesla coil that was critically coupled? Terman says
>> that is the point of maximum secondary current. This should give a Tesla
>> coil with the best possible output. Critical coupling occurs when the
>> primary circuit resistance is equal to the resistance of the secondary
>> circuit.  Also when:
>> 
>>   Rp = Rs  at critical coupling
>> 
>>   Kc = Lm/(sqrt(LpLs))
>> 
>>   Kc = Xm/(sqrt(XpXs))
>> 
>>   There are many possible TC parameter combinations that will give  Rp=Rs
>> but numerous related calculations are required. To my knowledge no coiler
>> has ever designed, built, and tested a critically coupled Tesla coil to
>> verify that the  Rp=Rs criteria gives an optimum TC.
>
>If one is talking about the static unloaded resistances present 
>as being Rs and Rp, it doesn't.  Surely the goal is get the energy 
>into the secondary as fast as possible and ideally in its entirety 
>before the gap wastes it all.
>
>Malcolm
>
>>   For coilers with the JHCTES program you may want to try the following
>> inputs that give Rp=Rs = 92 ohms, .21 coupling factor, 31% overall
>> efficiency, plus other output parameters for the design of the coil. It
>> should be noted that this feature of the program has never been verified.
>> 
>>   watts = 900    voltage = 15000
>>   pri cap = .01 uf
>>   pri rad = 4.3
>>   pri turns/inch = 4.00
>>   sec rad = 2.60
>>   sec turns = 255
>>   sec turns/inch = 13.00
>>   bare wire dia = .0201
>>   sec term pf = 11.00
>> 
>>   John Couture
>> 
>> -------------------------------------
>> 
>