# [TCML] primary-secondary tuning

Mddeming at aol.com Mddeming at aol.com
Thu Sep 10 15:10:04 MDT 2009

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Hi Brian,

theory under your belt of how and why Tesla Coils do what they  do, including
the safety sections.
Now, to answer some of the specific questions:
the 430+ KHz is the resonant frequency without any topload, while the 230+
KHz is the frequency with the topload in place. The significance of these
numbers is that maximum power transfer requires L1C1=L2C2,
and Fres= 1/[2*pi*sqrt(LC)].on each side.
A 15 KV NST has normal peak voltage of 21.2KV so 30 KV rating provides a
measure of protection, although some folks prefer a bigger safety margin.
As a general rule, you should not open the gap to more than 1 mm /2  KV
rms, or in your case 7.5mm MAX.

Check any of the basic theory sites to determine how to do the
calculations. For example: _www.richieburnett.co.uk_ (http://www.richieburnett.co.uk)
is a  good place to start.

Good luck,

Matt D

In a message dated 9/10/2009 8:52:21 A.M. Eastern Daylight Time,
brianh4242 at hotmail.com writes:

I am  coming along nicely with the design of my TC, and am using WinTesla
to help  with the calculations.

One thing I am not sure of is how the  secondary KHz and topload
capacitance relates to the tank capacitor/sg and  where to tap the primary.

Numbers given to me on WinTesla's  secondary coil (which I already made)
are:

Frequency: 430.78  KHz

1/4 wave: 571.21 ft

Frequency: 230.61 KHz  (why does it  list frequency twice?  is this the 1/4
wave freq?)

so - how do those numbers (or which of them) tell me  what the resonant
frequency should be for the primary?

I  am choosing a flat archemidies spiral from 1/4" copper tubing but want
to know  what length/spacing I will need and where abouts to tap it - so that
I can get  it in tune without an oscilliscope.  Some easier to understand
way of  plugging in the numbers and getting out whatever the matching
frequency should  be to resonate with the secondary.

I will be running it off a  15kv/30ma NST, so it sounds like i will need
about 30kv for the tank cap,  right?  How much does the microfarad rating of
the tank cap have to do  with the primary frequency, as compared to the spark
gap length?   I  don't have an oscilliscope so I want to get the numbers
right for best  performance.

And since radio shack has discontinued their power  conditioners (to
prevent backfeed into your house) does anyone else know where  to get them?  the
NST as you can tell runs at 450 watts max so .. like a  reverse surge
protector?  protects from surges coming into the appliance  as opposed to out from
the wall  socket

Thanks!
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Brian  Hall

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