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Re: Pigs and other barnyard experiments.

 Original Poster: "Bill the arcstarter" <arcstarter-at-hotmail-dot-com> 

Hi Bill,

Hey, I havenīt heard from you in while. Whatīs new on your side of the Earth?

My comments are spread thru your mail. 

 Next I measured the pig's no-load current by applying 120v to the 0-120 
 lugs (with a 65 mH limiting reactor in series to keep accidents down if 
 the HV side should flash over).  The no-load current was 0.69 amps, 
 which (assuming 90degrees phase angle) yields a calculated approx. 0.45 
 H of core inductance, a much more reasonable value.  Comments??
 Oh, the primary's resistance is on the order of 0.04 ohms, real real 
 tiny!

Comment: 
This sounds pretty reasonable. The DC resistance is of course (as on any power
transformer) very small. Itīs probably even lower than you measured, because
you will have to start taking the resistance of your DMMīs cables into effect.
 
 Then I tried a bit of Jacob's ladder action.  First I used my 0.065 H 
 limiting inductor in series with the pig's 120v input.  Note - this 
 0.065 H inductor is an un-shorted-out MOT primary.  The Jacob's action 
 was sort of erratic, but more strangely, each time I'd get an arc out 
 the HV side of the pig, I'd hear a "bump" coming from the variac and the 
 MOT. Is this normal???  I was powering the whole thing off a 10A variac, 
 if this makes a difference...
 Finally I tried using a resistive ballast, in the form of an old toaster 
 oven in series with the pig.  Setting the oven on "Toast" provided the 
 most power to the pig :) .  The Jacob's Ladder action was much much 
 smoother this way.

 I though most people had the best results when using inductive limiting.  
 This was not the case with me.  What is going on here?  Average current 
 using the toaster oven ballast was about 12 amps, and average current 
 using the MOT was something like 6-8 amps, although it swung around 
 wildly. In a previous experiment I'd determined that the V vs I curve of 
 this MOT core was rather nonlinear, ie, I increases rapidly with  increasing
V.

Comments: 

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 . It
is quite probable that your DMM was too slow to show the full current
"swing").

A resistive load (doesnīt have to be very large It could be quite a bit
smaller (in ohms) than the toaster you used)) sort of quiets this current
thump because it canīt follow this wild swing like your inductor can. A
Jacobīs Ladder lets you feel this thump quite readily because it cuts in and
out pretty hard. In a TC where your gap is firing more or less constantly the
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 didnīt do anything against you.... Did you really have to take a hatchet to
it?)

Lastly the variac lets you fine tune the setup. If you wanna go for the super
duper non plus ultra setup make your limiting inductor variable, too

coiler greets from that crazy dude in germany,
Reinhard