RE: Secondary size

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Luke" <Bluu-at-cox-dot-net> 

John:
OK maybe I missed some of what you were telling me out of frustration
from all the just do this answers.

I know this is not a formula per say but it is nice to have a response
with examples and then an observation of those examples that makes some
sense.
Thank you for the input.

And thanx for humoring me and my relentless questioning on the subject.

Luke Galyan
Bluu-at-cox-dot-net

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, January 15, 2004 6:42 PM
To: tesla-at-pupman-dot-com
Subject: Re: Secondary size

Original poster: FutureT-at-aol-dot-com

In a message dated 1/15/04 10:28:26 AM Eastern Standard Time,
tesla-at-pupman-dot-com writes:

 >Original poster: "Luke" <Bluu-at-cox-dot-net>
 >
 >Ok lets say the break rate will be 120bps
 >The power input will be 900watts (15KV -at- 60mA)
 >The expected spark length is 50"
 >How does one choose a secondary height from that?
 >Please do not just tell me what height to make it.
 >I want to hear WHY.


As can be read from my comments below, the coil would be
basically proportional in length.  The sparks in the example below
are 2.56 times the coil length.  Using this same proportion
would give us a secondary 19.53" tall for your proposed coil
example above.  The length to height ratio keeps this proportion
to keep pace with the voltage involved for the particular spark
length.  This proportion was found to be suitable at 120 bps
based on various coils I've built.  Actually I was able to push
the sparks to 60" using the 23" tall secondary, but occasional
racing sparks occured, so I was pushing things too far at that
point.  If a very large or very small coil is built, the proportions
may be different, I'm not sure.  Actually I just remembered I built
a smaller coil using a 12" tall secondary and was able to get
34" sparks before breakdown, so this does give a similar proportion.

Please understand that these ratios, etc., are approximate
figures.

John


 >thanx
 >
 >Luke Galyan
 >Bluu-at-cox-dot-net
 >
 >-----Original Message-----
 >From: Tesla list [mailto:tesla-at-pupman-dot-com]
 >Sent: Wednesday, January 14, 2004 3:26 PM
 >To: tesla-at-pupman-dot-com
 >Subject: Re: Secondary size
 >
 >Original poster: FutureT-at-aol-dot-com
 >
 >In a message dated 1/14/04 10:08:16 AM Eastern Standard Time,
 >tesla-at-pupman-dot-com writes:
 >
 > >The question is based on a particular anticipated arc length, what is
a
 > >good rule of thumb to decide on the HEIGHT of the coil?
 >
 >
 >Luke,
 >
 >It depends on the breakrate and power input and expected
 >spark length.  At lower breakrates which involve a larger
 >"bang size", the coil must be taller than for higher breakrates
 >which involve a smaller bang size for a given power input and
 >spark length.
 >
 >At 120 bps, I found it necessary to use a 23" secondary
 >winding height to obtain a 59" spark without coil breakdown
 >or racing sparks on the secondary.  At higher breakrates
 >the secondary can be somewhat shorter for the same spark
 >length.  The dimensions should be somewhat proportional
 >for larger and smaller coils also.
 >
 >John
 >