Re: [TCML] SSTC Coupling

[Steve Ward <steve.ward@xxxxxxxxx>]

Its just impedance matching, Greg.  I am not surprised with your results.

BTW, DONT use a resistor to limit power.  Just use more primary turns
(increase L pri) and reduce coupling (which in effect increases the
impedance seen by the primary).  Both turn count and coupling change the
impedance seen by the driver, hence the power consumption.

Steve

On Sat, Oct 24, 2009 at 8:19 AM, Greg Morris <gbmorris@xxxxxxxxx> wrote:

> Hi Folks,
>
> I've been doing computer analysis of SSTCs and I've got some results that
> seem to challenge the conventional wisdom of using the highest possible
> coupling when building Solid State coils. The coil I am building is
> required
> to use less than 500 W of input power, so I was experimenting with current
> limit resistors, and I noticed that depending on the value of the current
> limit resistance, the coil output characteristics can vary tremendously.
> With no limit resistor the output peaks when the coupling between the
> primary and secondary is between about 0.7 and 0.95 (See
> http://picasaweb.google.com/GBMorris/Tesla#5396152972495257298 ), but if
> the
> limiting resistance is 25 Ohm, the peak output is at the opposite end of
> the
> scale, between about 0.1 and 0.2! (See
> http://picasaweb.google.com/GBMorris/Tesla#5396152972060592098 )
> Increasing
> the coupling significantly *decreases* the output in this case. My circuit
> model can be found here,
> http://picasaweb.google.com/GBMorris/Tesla#5396152968071832514 , and has
> been largely borrowed from Figure 8-1 of Tilbury's book on Tesla Coil
> Design.
>
> Cheers,
> Greg
>
> --
> Greg Weyrich Morris
> VP External - Engineering Undergraduate Society
> B.Sc. Electrical Engineering (Final Year)
> University of New Brunswick
> G.B.Morris@xxxxxx
> www.unb.ca/robotics
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