Re : resistive V inductive ballast

Michael Tucknott <Michael.Tucknott-at-virgin-dot-net> wrote:

>Can some of you all knowing pig using guys please tell me what is the
>differance between resistive and inductive ballast.
>Steve Rodway has been using inductive ballast(1-5 MOT`s)and now Bill
>the arcstarter has been talking about resistive ballast, so what gives.
>What are the advantages/disadvantages of both.

First off - just because I do these things doesn't mean I necessarily know 
what I'm doing! :)

I built that largish resistive ballast since I think most folk who use MOTs 
and other smaller transformers as inductive ballasts run into the saturation 
problem.  Once the magnetic flux in the iron gets so strong it, in effect, 
ceases to have any influence or limiting effect on the current.  Thus the 
device strongly resembles a bunch of turns wound on air - ie - not much 
inductance at all! :)   Thus if you were to look on a scope at the drawn 
current - you would see sharp little peaks throughout the waveform. (gross 
approximations not withstanding)

With a resistive ballast, you know for a fact that the current will be well 
behaved and will stay sinusoidal w/o those large spikes, etc.

Now - maybe it doesn't matter in the grand scheme of things that these 
current spikes due to saturation are present.  I just wanted to try some 
high power stuff with smooth nonsaturating power.

I bet using a variable welder would be one of the best ways to do this, as 
welding xfmrs are designed to limit the incoming current with out 

Comments appreciated!
-Bill w/ 16kw variable resistive ballast

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