RE: [TCML] toroids instead of spheres - why?

["Phil Tuck" <phil@xxxxxxxxxxx>]

Yes Jason, you can do it by having the minor diameter large enough to hold
off breakout until almost full power is applied.

http://www.youtube.com/watch?v=3vKJyAycigQ#t=59   (That is an 8 x 34  inch
diameter)

The coil 'crackles' and buzzes until 80 - 85% + power is dialled in. Any
shortcomings in the coil will be exposed though, as it's under stress until
a streamer appears.


Phil

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Jason
Sent: Thursday, August 22, 2013 1:14 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] toroids instead of spheres - why?

While we are talking about toroids and spheres,

Whats the best way to work out size? and is there a way to only get the 
break out at one point with a traditional spark gap coil? I am using a 
break out point but still getting a dozen or so break outs

Cheers
Jason

On 22/08/2013 10:05 PM, Jim Lux wrote:
> On 8/22/13 4:48 AM, Scott Bogard wrote:
>> I'm not sure which document you are referencing, but if I am not 
>> mistaken,
>> a toroid typically has a larger capacitance for a given breakdown 
>> voltage
>> does it not?  IT also has far superior top turns shielding 
>> characteristics
>> which is why we use them so much; I believe this has to do with the 
>> E-field
>> shape though and not the capacitance.
>>
>
> Yes, toroids will give a more "uniform" field along the secondary.  An 
> infinite flat plate would be ideal, of course, but a toroid is a nice 
> way to get an edge on the flat plate while keeping the field at the 
> edge high enough that breakdown doesn't occur too soon, allowing more 
> charge to be stored.  You could have a Rogowski type profile on the 
> bottom of a sort of hemispherical electrode.  That's a flat plate that 
> has a rolled edge, where the field is greatest in the flat plate part 
> and gradually decreases.
>
> http://home.earthlink.net/~jimlux/hv/rogowski.htm
>
>
> However, for a given diameter, a sphere has larger capacitance than a 
> toroid.
> C(pF) for sphere is 4*pi*8.85*radius in meters.
> An approximate formula from Bert Pool for a toroid (sorry for the 
> change in units to inches) is
> C(pf) = (1 + (.2781 - d2 / d1)) x 2.8 x sqrt ( pi( ( d1 - d2 ) ( d2 / 
> 2 )) / 2)
>
> d1 = outside diameter of toroid in inches
> d2 = diameter of cross section (cord) in inches
>
> Some practical numbers.. a 36" diameter sphere has a C of about 50pF, 
> a 36" diameter toroid with 18" "tubes" has 35 pF capacitance. With 8" 
> tubes (and a 20" disk in the middle) about 39 pF
>
>>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2013.0.2904 / Virus Database: 3211/6594 - Release Date: 08/20/13
>
>

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla