Re: [TCML] BIGPIG secondary dies...but may be resurected

[bartb <bartb@xxxxxxxxxxxxxxxx>]

I think Ed is correct. According to models, the larger the top load is 
relative to the coil size, the "less" the current changes from top to 
bottom. But if a bare coil, it is max to zero (or near). Also, the 
linearity of the distributed current along the length of the coil is 
dependent on the h/d (more linear for low h/d coils).

For the normal h/d of 4 or 5, it's not quite linear, but curved even 
with bare coils. Throw a big toroid on the coil and the current is far 
less changing from bottom to top because the toroid is very well adapted 
at forcing itself (it's C imposed on the inter C of the windings) and 
changing the overall distributed capacitance of the coil due to the 
toroid geometry. The current as a result becomes less changing from 
bottom to top (but there is still a difference). So no, current is not 
the same from end to end from a technical stand point. And it can never 
be the same unless you throw turn to turn C out of the equation.

If you make a statement as "the top current is smaller than the bottom 
current", then you would be correct. The problem is the person stating 
this usually does not know "how much smaller". In rare cases, it can be 
a lot. In most TC cases, it's not a big change. If I were to give a 
"number", I would say the current on average coils is about 25% less at 
the top than it is at the base. But, that's just truly rough guesstimate 
of what I would call average coils and average tops to coils size.

Take care,
Bart

Ed Phillips wrote:
> It's a long piece of wire with capacitance between turns and 
> capacitance of each turn to the surroundings.  Current distribution 
> depends on how much top load capacitance is on the coil.  With no top 
> loading the current will be lower at the top; if there are no 
> streamers the current should be essentially zero at the top.  
> Distributed capacitance is the culprit.
>
> Ed
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