Re: Secondary size

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

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