Gentlemen,
I am not an electrical engineer but have worked around machinery in power
plants all my life.
I also worked in an electric motor rewind shop while I was in school, not
bragging or complaining just being open about were I am coming from.
I have a 10 kva pole transformer that I intend to use to drive a good sized
coil. I have assembled a power supply for the transformer with four variacs
so I can vary the voltage up to about 290 volts with a 240 volt supply.
I constructed a ballast from three golf cart battery chargers by combining
the lamination's and winding a coil for the center post.
The lamination's are E and I shapes. The E lamination's were welded
together and the I lamination's were welded together in the chargers and
then the I lamination's were welded to the E lamination's after the charger
coils were installed.
I was able to carefully grind out the welds between the E and I and bolted
three sections of E lamination's together and three sections of I
lamination's together to make a core that has about 12 square inches of the
center post of the E lamination's.
The core weights about 40 pounds. I wound a coil from three parallel number
14 magnet wire because I could not get number 8 wire.
I have about 118 turns if I remember correctly. By adjusting the air gap
between the I lamination's and the E lamination's I can vary the current
from about 20 amps to, I have it at 42 amps for now. It is quite and does
not heat up at all. The air gap is about 0.700 inches at that current. I
have not yet completed the tesla coil and have only used the pole
transformer to drive a 10 foot traveling arc.
I say all this because the amps were the lowest when the air gap was zero
and the amps were reduced as the gap was made larger.
This tells me that your problem is not that you do not have enough copper
but that you do not have enough iron.
Both the Phils use large iron cores as does Richy Burnett.
On Tue, Dec 18, 2018 at 7:38 PM Tyler LaVite <tlavite@xxxxxxxxx> wrote:
> NSTs or MOTs but good luck they smoke out in mere seconds. I built a
> ballast by winding 500 feet of 10 gauge THHN around a 2 inch piece of PVC
> and could adjust the current draw by adding or removing welding rods from
> the inside of the PVC pipe. It worked quite well and had a decent duty
> cycle but the problem was the pipe would get hot from the rod heading up
> and it would want to sag. Could build one like that and submerge in oil.
>
> Sent from my iPhone
>
> > On Dec 18, 2018, at 7:57 AM, Daniel Kunkel <dankunkel@xxxxxxxxx> wrote:
> >
> > Tyler and David,
> > Yes, as much as I hate to give up more valuable floor space in the shop
> to
> > another welder, it seems inevitable. I will get one someday, but I am
> > waiting for something priced so right, I can't say NO. So in the
> meantime,
> > I just need to scrounge up an additional 3.4 mH of inductance using stuff
> > around the shop. Hence the old NST core idea, which is not heavy, does
> not
> > take floor space, and has no additional cost involved.
> > ~Dan (streamers on a budget)
> > Kansas City area
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