purpose of a variac?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Qndre Qndre" <qndre_encrypt@xxxxxxxxxxx>

Hey coilers,

I've read several documents on the internet which claim that the 
power throughput of a TC can be adjusted using a variable transformer 
to power the supply transformer of the coil. I don't see how this 
could be done under regular circumstances. If the input voltage of 
the supply transformer is reduced, it's output voltage reduces as 
well. The voltage across the capacitors can never exceed the supply 
voltage (unless you use resonant charging which may destroy the 
secondary winding of your supply transformer). Since the spark gap in 
the tank circuit is best to be tuned just to fire at the absolute 
voltage peak for optimized performance it will never fire with 
reduced input voltage to the primary circuit.

Regards, Q.