RE: What do I do ?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Rich & DJ" <rdj@xxxxxxxxxxxx>



Subject: Re: What do I do ?

Original poster: "Christoph Bohr" <cb@xxxxxxxxxxxxxxx>

Hello Rich.

 > I am trying to get a transformer and ballast set up with just a spark
 > gap for now. It is multi gap copper tube set up, 8 tubes total, 5
 > tubes in use @ .050 each .200 gap.
hm, would nice to know the type of transformer for better help,
but this is of course possible... Transformer is a standard EI core 240v
in 13Kv out, Tag says 1.95 Kva, it is non NST , no shunts or current
control.

 > The first ballast try was with a roll of 12 ga w/steel core and a NST
 > transformer core with just the primary,
both in series configuration? If you have an unballasted transformer in
you
setup, you can do the following: connect only the ballast across your
variac
and measure the current, modify the ballast until you reach the
desired current.
This will be (pretty much) the propper setting for your setup with
you transformer
connected, cause the transformer will add zero Ohms to the loop when its
output
is shorted out by the arc.


 > when I ramped up the supply
 > voltage it would barely fire when I got up to 95% on the voltage at
 > the transformer input. I added 7 turns of 10ga for a secondary on the
 > NST core, now I get good sparks at 60% voltage.
 > Can any one tell me why ?
when you add a shorted turn or winding to the core, this will lower the
over
all inductance of the ballast, this increasing current. You might as
well add
an airgap or remove primary turns or withdraw the steel core from the
wire spool. The steel wire core was made with thread all in the center
so I can do this.

 > I am using the roll of wire and NST core to limit my transformer to
 > 1.95Kva max. It is all trial and error at this end , should I add
 > more turns on the NST secondary until I get null spot.
More turns won't lead to more current, rather less turns but with 7
turns
you are already pretty low. You can try to remove some of the steel core
in your other ballast. I am not sure what NST you have and whether it
will be able to supply 1.95KVA at all, the wire spool probably will...
Why 1.95KVA?  just curious.... Well the tag says it is rated at 1.95Kva


 >   I am getting actual  8 amp at the input of the transformer at 140v
 > , max s/b 8 amp at 240v.
140V is probably a miss-measurement. With open load there should be
almost 240V at this end and with shorted output zero.... thats what the
ballast ist for. You simply need less ballast inductance and you are
done.
Exact values might differ, as the devices are not mathematicaly perfect.
I have a good Simpson panel meter and a cheap DVM on it now, I have a
good Fluke RMS DVM but I am protective of it and now realize the $3
meter might not give good voltage readings


regards

Christoph Bohr