* Original msg to: Esondrmn-at-aol-dot-com

Quoting Ed Sonderman:

 ES> Richard,

 ES> Yesterday's discussion brings up a question.  Can you expect
 ES> comparable performance from a Tesla coil system with a 9kv   
 ES> 200ma (1.8kva) transformer or a 15kv 120ma (1.8kva)          
 ES> transformer?

Good question. Part of the art of synergistic tune in Tesla
systems involves matching the tank circuit capacitance value to
the available energy from the step up transformer during one half
of a 60 cycle waveform (1/120th of a second). With static gaps in
the tank circuit the capacitor cannot process any excess energy
from the supply transformer once the capacitor is fully charged. 

The feed voltage from the step up transformer makes a huge
difference to the value of the capacitor used in a matched tune. 

A 9kv 200ma power supply will fully charge a .059 uF capacitor in
1/120 of a second, where a 15kv 120ma power supply will only
charge about a .02 uF cap.

Suppose you had a coil with a .059 uF capacitor in the tank
circuit. Using your 9000 volt power supply you get a "match"
at 200ma, or an input power of about 1.8kVA. 

Now, you boost your input voltage up to 15,000 volts with your
.059 uF capacitor (assume the cap will withstand the voltage).
Your capacitor will hold much more energy: it will take 330ma 
of rms amperage from the power supply to fully charge this
capacitor in the same 1/120 of a second. Your input power has
gone from 1.8kVA at 9000 volts, to damned near 5kVA at 15,000
volts (15kv 330ma), more than double the power processing ability
of the same value cap at 9000 volts.

For this reason, most coilers end up going to higher voltages to
get greater peak powers. The problem is the capacitors have to
hold up to these higher energies, but another advantage gained is
that capacitor value will remain the same, OR GET SMALLER!

 ES> Is there a certain minimum input voltage necessary?

With an ordinary static spark gap you need about 7000 volts to
get a good reliable tank circuit. If the voltage drops much lower
some special spark gap designs are almost a necessity.

Richard Quick
... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12