```Boris Petkovic  wrote:

> Has anybody tryed experimenting Tesla's scheme 4 for primary circuit -
> 1899. -scheme 4?
> I'm curious about it since lows of transients of lumped circuits
> doesn't support formulae and great parts of text at all, but Tesla's
> words of "little current through the spark gap and big through LpCp
> circuit" are very important (smaller losess in prim.circuit,more
> succesfull quenching).If that assumption (while rotary employed)is just
> partialy correct in praxis -I think it is worth of checking out.

That circuit is a case of "triple resonance", similar to a magnifier.
Note that the circuit can be drawn in this way, with the gap closed:

k12
+---L1---+---+   +---+
|        |   |   |   |
C1       Cp  Lp  Ls  Cs
|        |   |   |   |
+--------+---+   +---+

This is a magnifier model drawn backwards. The energy oscillates
periodically between C1 and Cs, starting from C1 instead of from
Cs in the magnifier, using the "descending" parts of the beats
instead of the "ascending" parts. The formulas for the
triple resonance optimum design apply directly (and Tesla's equation
II is not correct for optimum design).

Example, if you want to simulate:
Mode 345, base frequency: 100 kHz
Energy transfer in 5 us, in 4 semicycles of 400 kHz
Voltage gain: sqrt(C1/Cs)=31.6
Cs=10 pF
C1=10 nF
Cp  81.27 nF (!)
Ls  18.05 mH
Lp  2.216  uH
L1  15.83 uH
K12 0.3504

With most of the primary capacitance in Cp, the current through
the gap is really small compared to the current through Lp.
The main price is more capacitance at the primary circuit.

See the formulas at: http://www.coe.ufrj.br/~acmq/magnifier.html

Antonio Carlos M. de Queiroz

```