Re: Primary coil configuration

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Chris,

Hi coupling is not necessary with TC's.  In fact, it can be too high 
and cause racing arcs along the secondary coil.  The primary is RF 
tuned to the secondary/topload resonant frequency so the enery will 
transfer to the secondary over 5 or so RF cycles (depending on the 
k).  Given that, people wind flat spiral primaries to keep the 
primary as far away from the HV stuff as possible.  If the primary 
were placed midway up on the secondary coil, there would be flashover 
between the two.  Also when you get high enough power, there can 
often be secondary to primary strikes and is why people use grounded 
strike rails to keep the hits off the primary.  You may want to check 
this site for excellant theory writeup on TC's:

http://www.richieburnett.co.uk/tesla.shtml

Also, you can check the Terry Fritz site to see my pictures of how 
the secondary can strike what you dont want it to:

http://hot-streamer.com/temp/GerryReynolds/15KV_120ma_SRSG/

Congradulations on your chosen EE career.

Gerry R

> Original poster: "Chris Farmer" <cfarmer@xxxxxxxxxxxxxxx>
>
> Hi All,
>    I'm in the process of designing my first coil.  I'm a junior in 
> EE and it just caught my intrest while I was researching HV 
> transmission lines. I have a 15kV 60mA NST and I'm reading as much 
> as I can about the rest of the design before I actually buy/build anything.
>    My question is what is the difference between making the primary 
> wind outward away from the secondary opposed to winding vertically 
> keeping the windings all the same distance from the 
> secondary.  Also what does primary placement around the secondary 
> effect.  If I move the primary up to the middle of the secondary 
> what will that effect?
>
> ~Farmer
> Durham NH