RE: Secondary size

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

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

Thank you for the input.
So why can a small dia secondary handle only so much power?
For example your 6" coil designed for 15KV 120mA what is happening that
causes the near destruction running it at 600mA 15KV?
Not that I need exact formula's but what is happening?

And thanx never really understood why some used a double toroid on the
top.
Ill look more into that next I guess.
So you might see some questions related to that soon.

thanx

Luke Galyan
Bluu-at-cox-dot-net

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, January 14, 2004 3:29 PM
To: tesla-at-pupman-dot-com
Subject: Re: Secondary size

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

In a message dated 1/13/04 7:03:33 PM Pacific Standard Time,
tesla-at-pupman-dot-com writes:


 >I would assume that the height would be based on anticipated arc length
and
 >the dia would simply fall into using what you can to stay in the
suggested
 >height to width ratio.
 >How do you go about deciding how tall the coil should be based on the
arc
 >length?
 >Other than aesthetics what is the method for choosing a secondary size?
 >What is the cut off for deciding how short a coil can be with a given
 >anticipated arc length?
 >
 >It seems there are coils that generate longer arcs than the coil is
 >high.  And since the arcs are referenced to ground it seems that is
putting
 >the top load very close to ground with respect to its output.  I know
that
 >the toroid slash secondary top will be at the same positive or negative
at
 >any one time as the arc and like charges repel so that is what keeps
the
 >arcs from going straight down.
 >
 >
 >Ok also if a height is determined what are the advantages /
disadvantages
 >for going with the larger diameter coil verses the smaller diameter?
Keep
 >in mind that when I say large or small diameter I am talking about
staying
 >close to the excepted rule of thumb for height to dia. ratio.
 >
 >Thanx
 >
 >I will be asking lots more questions so bare with me.  J
 >Luke Galyan
 >Bluu-at-cox-dot-net


Luke,

My opinion here, and there are lots of them.  There are no set rules,
you
can make just about anything work.

The diameter of the secondary form should be selected by determining the

maximum input power level you plan to use.  For example my 3" dia.
secondary coil uses a 15 kv 60 ma power supply.  This coil could take
more
power but not more than 2 or 3 times I would not think.  My 6" diameter
coil was designed with the idea of using a maximum supply of 15 kv 120
ma.  I am now using it with a 15 kv 600 ma supply and it is close to
destruction every time I run it at full power.  It has a winding length
of
27.6" and produces sparks of 104" - which is 3.7 times the winding
length.  This coil would perform much better if I rebuilt it with say a
10"
dia. secondary.

So, decide on your power supply.  Then select the appropriate diameter
secondary form.  The higher the power, the larger the secondary you will

want.  Say you want to use a 5 kva to 7 kva supply like I am using.  I
would go with an 8" to 10" diameter secondary.  If 8", then at 4.5 or
5.0 :
1 winding length, you would want a winding length of about 40".  Make
the
form about 2" longer on each end than this or about 44" total length.
For
about 1200 turns of wire, you would want to use # 20 wire.  Actually #
20
heavy build is about .0351" in dia. which is about 28.5 turns per inch
which would be 1,140 turns total.  Or use # 22 wire and get about 1,400
turns which would probably be better.

I advocate using a two toroid system on the secondary.  One to provide
corona supression for the top of the secondary windings and a larger
elevated toroid above that to get the sparks up away from the primary.
You
can see a picture of this at my web site under six inch coil.

http://members.aol-dot-com/esondrmn/index.html

Ed Sonderman