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Re: I'm going to need help with a 34kV power supply



Original poster: "Chris Brick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <cbrick-at-rebelbase-dot-com>


>Greetings, all!  :)
>    A while back, I got my hands on a 34kV 120ma pulsed DC power supply from
>a laser assembly.  To date, I've only ever used it in a jacob's ladder and
>it was able to span a 7" gap pretty easily.

You got that little guy from me.  Glad to hear you are going to use it on a 
coil.  They do make for a pretty serious jacob's ladder supply.

>    That said, I'm now itching to use that pretty gold box to power a larger
>tesla coil.  I realize that the extremely high voltage from this power
>supply is going to cause some major design problems with the primary
>circuit.  I have enough pulse caps to hold off 140kV and give me 7.5nf.  The
>caps will obviously have to be immersed in oil, the connections and wiring
>between all of the components will all have to be heavily insulated and
>probably coated with an insulator to keep corona losses down, but I'm not
>sure about the construction of the primary coil.  I'll most likely use 3/8"
>copper tubing, but how far apart should the turns be spaced?.

The power supply has a variable voltage output.  They are current source 
power supplies so the current level will start off high and as it reaches 
the set voltage, the unit will stop charging.  If I understand this 
correctly, it will push the current out as fast as possible until the 
voltage setting is reached.

I am currently using 4 of these supplies in parallel on my large coil 
system.  Initial testing has produced some 15ft arcs to the ground from my 
9ft tall coil.  I am currently running NO protection devices.  Just the 
power supplies directly to the tank circuit.  So far so good but protection 
circuits will go in before long.  It appears that there is a large diode on 
the HV output terminal.  I need a larger, smoother toroid and to do some 
major tuning but the results are very good so far.

>    The spark gap is another problem.  I'd like to use an async rotary with a
>good bit of radial velocity (3450rpm, instead of 1725rpm), but what would be
>good to use for the stationary electrodes so that they won't glow with
>corona and ionize the air around the gap excessively?  Would a nice fan take
>care of that, or should something like a small doorknob be used?
>    If I go with a static gap, I worry about corona losses at the edges of
>the copper pipes, if copper pipes are the best choice for this gap.

I am using a sucker single static gap at the moment (Gary Lau style).  It 
works very well.

>    How do you feel about a triggered gap?  The trigger electrode would have
>to be powered with a significant amount of voltage, given that that tank
>circuit will be powered with a 34kV power supply.

I am planning to build a triggered gap for my coil but will hopefully be 
able to design a controller that will allow variable breakrate since there 
is no 60hz wave in the tank circuit.

>    Any advice on how to properly design and build such a high-voltage beast
>would be greatly appreciated.  I won't mind comments about safety, either,
>as I don't want to miss any issues on safety just because I hadn't
>remembered them at the time.

Like I said above, you can limit the voltage to the coil at the 
controller.  I love running a coil from a little plastic box with few 
switches and a potentiometer.

Since these power supplies use ground as one side, one side of the tank 
circuit must be connected to ground.  On my coil, this is the bottom of the 
secondary, inside turn of the primary, and one side of the spark 
gap.  After running the coil, I have to place a resistor network across the 
cap bank to make sure there is no charge left .  This is something you may 
need to do also.

For anyone interested in some pictures of the power 
supplies:  http://www.teslacoils-dot-org/rcs1000/index.html

I will have my new website up in a short while with lots of pictures of my 
big coil as well as some text about the whole project.

Chris