Re: [TCML] Burn Through The Stem Of The Globe?

[DC Cox <resonance@xxxxxxxxxxxx>]

How long are your run times?   In museum applications, sometimes they run 5
days a week and 8 hrs per day.
I've had some burn thru after 6 hrs of run time or less.

Of course, if your driver is failing then this would allow the stem to cool
a bit.

Dr. Resonance




On Sat, Jan 17, 2009 at 1:41 PM, miles waldron <mileswaldron@xxxxxxxxxxx>wrote:

> 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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