[TCML] Burn Through The Stem Of The Globe?

["miles waldron" <mileswaldron@xxxxxxxxxxx>]

Really? I am using a ZVS IGBT flyback driver on my large plasma globes,
14-inch, mark dunns, and the ball will actually throw small arcs into the
air < 1 inch. At max power of around 100Watts, the Xenon globe is quite
impressive, multiple tendrils, fractal breakout, etc. I use a thermal type
fuse that trips and then recovers if any drain current becomes excessive.
The driver circuit can go completely haywire, and just shut itself down
without blowing up any parts. Most of the time it just cools down, resets
itself, and keeps on running. I think any driver will just sometimes go
crazy because of EM fields around the flyback, and so you have to build
"resettableness" into the driver. I don't use any resistor into the globe,
it is just hotwired to the flyback, for maximum current, and maximum
beautiful output. I also don't use a gapped core flyback.

I am just mentioning, there are other arrangements that function well under
duress.

buildingthefuture@xxxxxxxxxxxxxxxxx


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of DC Cox
Sent: Saturday, January 17, 2009 12:23 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] op amp wiring


First, don't use the 555 to drive a 2N3055.  This design is not robust
enough to do the job.  Use a single transistor BUF420M (Digi-Key).  It rated
something like 60 Volts at 30 Amps and will almost never blow.

Fuse the DC part of your circuit also.  Use a fast acting instrument fuse so
any shorting will blow a fuse and not your component.

Be very careful if you elect to use a MOSFET driver for a plasma sphere. The
MOSFET design is much more efficient and provides excessive current on the
HV output of the flyback --- enough to burn thru the stem of most any globe
if not controlled.  With our MOSFET design we always use some 10 kV 100 meg
resistors in series with the output to prevent this.  Personally, I prefer
the BUF420M design as it delivers approx 1 mA to the globe --- not enough to
burn the stem thru.

Be sure to use a "gapped core" flyback to prevent excessive sec current.  I
gap at 4 mils on each side of the core.

Dr. Resonance


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