Re: 8 kHz Tesla Coil

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FIFTYGUY@xxxxxxx 

In a message dated 9/23/05 1:45:10 PM Eastern Daylight Time, 
tesla@xxxxxxxxxx writes:
No comment is a waste of time in the persuit of knowledge and
truth.  I think I understand what you were getting at.   If one uses
a wire size where the current density is low in the center (that I
called a waste of copper), one might opt to fix that by using a
smaller guage and this will result in an increase of AC resistance.


    Like I had posted before, using a solenoid coil optimization 
spreadsheet, we found the optimum wire size (for minimal losses, 
assuming CW operation) occurred when the DC resistance was equal to 
the skin effect. Trying to improve one hurt the other, at least 
within the bounds of normal TC parameters.
    Also found optimum turns to be around 1500, but this was only 
10% better than 1000 turns (but at 50% more wire/form cost).
    Malcolm - WRT to your question a few months ago: I finally dug 
out that spreadsheet, and no, it did not account for proximity effect.



One question unresolved in my mind is how important it is to have the
optimum unloaded Q considering that once breakout starts, the coil
becomes loaded and Q drops to a low number.  Is the issue just one of
power dissapated in the wire or are there other issues???


    Simple experiment? Insert a suitable Q-killing resistance in 
series with the TC secondary, and see how it affects operation. Maybe 
big composite low-inductance power resistors at the top and the base? 
RF lossy coilform? If people successfully use things like Sonotube 
for coilforms, it can't be that important.
    But how important is high Q with a DRSSTC, when you're trying to 
ring up voltage in the secondary in minimum time before breakout?

-Phil LaBudde