# Re: [TCML] Question for solid-staters

```Hi Ken,

```
A Primary:Secondary k of 0.4 may be somewhat problematic from an insulation standpoint. It's comparable to the coupling used in magnifier driver transformers, and these can be prone to P:S flashovers with air insulation.
```
```
Try loosening the P:S coupling to 0.2 - 0.3 and extending the simulation time to 2-3 msec to allow the secondary to ring up over a longer time. You may be able to achieve similar voltage output without the need for excessively high coupling coefficients (and potentially heroic field control and insulation techniques).
```
Bert

Ken Herrick wrote:
```
```More accurately, Re: Question for single-resonance solid-staters--of
which there seem to be mighty few still around.

Having been involved in deciding on series or parallel single-resonance
with synchronized primaries (from secondary feedback), I've received
good advice recently but have thought to make a simple simulation to
further pursue it.  Ref. the following link.

https://dl.dropboxusercontent.com/u/28799314/TCRB3/KCH-Screenshot%20-%204_24_2015.jpg

Two anti-phase drives of 300V each drive 2 identical primary coils. The
transformer is a simulation of a Tesla coil (with the secondary
inductance of my actual coil) and its top-load.  The secondary Fr is
what's calculated for those L & C values--absent any primary influence.

In the chart, I started out at primary:primary k = 1 and
primary/primary:secondary k = 0.8.  Ran a 1ms simulation, measured the
maximum, entered that into the chart, etc.  Finding 35KV as the maximum
in that column, I proceeded leftward then upward similarly, reaching the
sweet spot of the one k = 0.9 and the other, 0.4.  I then set R1 to
100K, just the once, and ran that again.  That seemed to show that
paralleling primaries closely together and setting a rather loose
coupling to the secondary yields the best response (and the easiest way
to do it).

I just note I made an error on the chart, substituting +144K for *144K
in the notation.  Won't bother changing it...

This seems to further tell me that I don't have to series the primaries
to create 1 effective coil but rather can configure them just physically
& electrically in parallel.

KCH
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```
```
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