Re: purpose of a variac?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>


A second (separate) variac is used in series to adjust the current 
independent of the voltage (first variac).

Dr. Resonance

> 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.