Re: [TCML] Toroid question

["Dex Dexter" <dexterlabs@xxxxxxxxxxx>]

Yes Bart,the problem of too small toroid is  usually met in common practice.Too big toroid is a rare problem :).

Dex

--- bartb@xxxxxxxxxxxxxxxx wrote:

From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Cc:
Subject: Re: [TCML] Toroid question
Date: Sun, 31 May 2009 08:59:38 -0700

Hi Jim,

What you mention is very common practice and probably good advice to 
ensure breakout (but not necessarily performance). Coils have been built 
with toroids whose minor diameter is quite a bit larger and they worked 
fine. For example, I use a 6.5" minorD on my 4.5" sec. I also used a 9" 
x 30" toroid on the 4.5" sec when I hooked it up in the hybrid maggy 
configuration. I believe power and bang size are major contributors to 
the performance of a top loads ability to perform well run well. As long 
as the top terminal is sufficiently charged so that the surface field 
strength achieves breakdown in relation to the surrounding.

As Gary points out, we really don't have good hard numbers to predict 
exactly when too big is too big. Considering the cost and/or labor of 
toroids, it is something we should attempt. I personally have an 
academic problem with toroid sizing. To relate a toroid size based on a 
secondary diameter will not be best for all cases. It's simply an 
empirical probability that many coils will do ok with, so it  does 
become good advice from that standpoint only.

Take care,
Bart

Jim Mora wrote:
> Hello List,
> I seem to remember reading 2 thirds the winding length or a bit more as a
> guideline for the major diameter. I have had pretty good results with a
> minor diameter (which has a major effect on the capacitance if the major is
> not oversized) close to the secondary diameter. Can anyone concur with that?
> Jim Mora
>
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
> Of Lau, Gary
> Sent: Saturday, May 30, 2009 2:37 PM
> To: Tesla Coil Mailing List
> Subject: RE: [TCML] Toroid question
>
> Yes, there surely is a topload size that's too large for every coil.
> Unfortunately no one has yet discovered a means of predicting what that size
> is, so all we have is some very crude rules of thumb and trial and error.  
>
> When a top load is too large, it doesn't just make the sparks smaller; it's
> an all or nothing proposition.  Beyond a certain size, the topload simply
> won't break out - even with a breakout point.
>
> Regards, Gary Lau
> MA, USA
>
>

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