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Re: Variac setting (Was Rd: Rotaty popping)


>
> Original Poster: Esondrmn-at-aol-dot-com

Hi Ed, 

In this reply you made to John, I noticed your variac setting and reaction to
change is **identical** to my variac setting and reaction. I too have little
change in performance with movement of the wiper to about 25% or so. I also
find my best performance just about center of the variac. This makes me wonder
why we are seeing such a similar reaction. I believe we are both using a variac
and series resistor combo (my smoothing resistor is 2.5 ohms). I wonder if
others using this setup with a pig or potential xfmr are seeing the same type
of reaction? I find this fascinating - because I don't understand why. Your
ballast is a 40A and my ballast is 30A. BTW, I measured my variac (setting at
mid winding) at 11.2mH. I would assume yours is a bit more (maybe 16mH or so). 

Does anyone else see this similarity? Does anyone have a theory why? 

Bart 
>
> As an addition to an earlier reply of mine, I am a couple of days behind here
>
> - the 5,000 watt variac that I am using as ballast for my 5kva transformer, I
>
> believe is saturating.  It is rated for 120 volts, 5,000 watts which should 
> be good for about 40 amps.  My typical primary current is around 30 amps.  It
>
> does groan a little however.  I really don't want to cut the core.  An 
> interesting thing to note is that the best performance from the coil does not
>
> come from a particular tight setting on the ballast variac.  I now have it 
> set about in the center, and it really does not change the performance if I 
> move it either way up to maybe 25%. 
>
> Again, the reason I went to the variac instead of the welder was to prevent 
> an unwanted 60 HZ resonance that was causing extremely high primary voltages 
> and destroying my caps.  The variac also fixed the problem of the popping 
> sound in the rotary.  My original configuration with the welder and using 
> about 1.5 ohms of series resistance also seemed to run better at lower welder
>
> settings, which would be with higher inductance.  I haven't measured the 
> inductance of the variac, but I would guess from looking at it that it would 
> be considerably less than the welder. 
>
> Ed Sonderman