RE: [TCML] Secondary Coil: Wire Gauge and Number of Turns

["Phil Tuck" <phil@xxxxxxxxxxx>]

Brandon,
Not too sure what you meant by "(... while keeping the required primary
inductance to about 90% of the primary coil's capacity.)". 

Opinions vary, but too high a secondary inductance will result in resistive
losses and a low 'Q' value (<200), while too low won't allow the secondary
to develop enough top volts. Aiming for as "high as possible" is probably
not the way to do it. As a "high as possible" approach will throw up other
issues elsewhere in the design. 
I wanted 80 odd mH for the last coil I wound (quiet high for the size), and
while I could have achieved even more by using a different turns / gauge
setup, I avoided going too high as apart from resistive losses, the
secondary inter-turn capacitance also increases with turns, which is
something you don't want.
Some people space wind to keep the secondary capacitance down, but then you
don't maximise the inductance for your chosen secondary winding space and
size (maximise not being the same as 'high as possible' though)
 It's all about having a balance, that's why using an aspect ratio that has
been determined as sensible by countless coilers over the years (4 / 5:1),
combined with a turns ratio centred around 1200  (900 - 1500), means the
both the secondary inductance and inter-turn capacitance should work out ok.

If you were using an RQ gap, which can have higher losses, rather than your
proposed SRSG, you would need to keep the primary turns above (say) 12, but
with a SRSG that has less losses, you need not be so worried if the finished
design gave you (say) 9 or 10 turns.

Use Javatc for the design and post the output.

Phil (UK)

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Brandon Hendershot
Sent: 01 July 2013 22:12
To: Tesla Coil Mailing List
Subject: [TCML] Secondary Coil: Wire Gauge and Number of Turns

I've been punching numbers into TeslaMap for a while trying to design my
next secondary coil. I know the idea is to get the Inductance as high as
possible, but the conflict with that is ending up with more and more turns
as you raise the inductance. I know that the AC resistance of the wire is
going to be a bigger issue with more turns. Acceptable values I've heard
are 1000-1500 turns.

How critical is this range? My designs tend to come out with 1650-1800
turns.

Another factor in design is the wire gauge. The thinner the wire, the more
energy is lost to resistance according to Ohm's law. The thinner wire also
allows the inductance to be higher given a limited winding height. I'm
really not sure which way to lean in balancing that out... More inductance
vs more resistance (I suppose the power put into the coil helps determine a
minimum).

I'm hoping to build with 27 or 28 gauge magnet wire

Coil is running 1825 Watts (15/120 NSTs), 120 BPS SRSG, 0.25 x 0.25 x 14
turn primary (7.5" Hole), 55nf Tank Cap

(Some of my design parameters: Stick close to a 4:1 ratio, 6.1-6.6" Width,
24-29" Height, while keeping the required primary inductance to about 90%
of the primary coil's capacity.)

Hope you can help. Thanks!

- Brandon H.
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla