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Re: Pigs and other barnyard experiments.

Reinhard wrote:

>Hey, I haven=B4t heard from you in while. What=B4s new on your 
>side of the Earth?

Not much.  Just bought a 110,000 BTU kerosene heater.  Maybe this winter 
I'll actually be able to keep coiling out in the garage when the temps 
go down! :)

>My comments are spread thru your mail.=20
>
>This sounds pretty reasonable. The DC resistance is of course (as 
>on any power transformer) very small. It=B4s probably even lower 
>than you measured, because you will have to start taking the 
>resistance of your DMM cables into effect.

Nope.  Already accounted for that! :)

>The most versatile limiting setup is:
>
>a.) An inductor
>b.) A resistive load
>c.) A variac
>All connected in series with your pigs input.
>
>A pure inductor will give you an erratic output on larger loads (i.e. 
>your pig). This is because under no load your inductor will only pull 
>the needed magnetizing current. If you now put a non constant load 
>(Jakes ladder) across your pigs output, the current pulsates every 
>time your gap fires. This change in the magnetic field is the thumping 
>you are feeling. The current you measured (6-8 amps) with your 
>DMM was only a guesstimate of your DMM (i.e . Itis quite probable 
>that your DMM was too slow to show the full current "swing").

I used a clamp-on analog ammeter, so it should be fairly smoothed over.  
Don't know if it'd show average or rms however...

Seems that, according to what folk have posted, that my limiting 
inductor is much much too large in the Henry department!  Most people 
seem to use 6-10 mH typical. I tried using my ~50 mH MOT unit.

>thumps will be less prononced. If you let me make a wild guess it 
>would probably be smoother if you just short out the secondary of 
>the MOT (That is if it still WAS there. If I recall you "hatcheted" it 
>out. Poor copper wire. It didn=B4t do anything against you.... Did 
>you really have to take a hatchet to it?)

Yes, I really had to!  It was in the way.  I hatcheted off the 
secondary, and drove out the shunts.  This way the core has a nice large 
open window, just right for rewinding to make a tapped inductor.

I also need a smoothing inductor for my tig welder - and I'm hoping 
these cores will work.  Need maybe 2-3 mh at ~100 amps...

PS - removing the shunts didn't change the fact that the primary draws 
about 6 amps at 120 volts...  Works out to 0.053 H, if it is not 
saturating (to be determined later...)

But don't worry.  I have about three more unhatcheted MOTs and I know a 
place whre I can get more for $5/ea off the shelf...

I'm also told you can make nice limiting inductors out of the outer 
shell of a nead induction motor.  You loop your wire in one end of the 
shell, out, and around a few times.  There's no substitute for iron, it 
seems..

>coiler greets from that crazy dude in germany,
>Reinhard

...and I am know as:
-Bill the arcstarter
Starting arcs in Cinci, OH
http://www.geocities-dot-com/CapeCanaveral/Hangar/6160


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