Re: to the flyback transformer question (fwd)

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Date: Wed, 13 Oct 2004 23:38:53 -0400
From: Jack Vandam <snotoir7674g@xxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: to the flyback transformer question

First of all, my apologies as I accidentally deleted your original message
asking about flybacks.  I'll try and provide a bit of info since I have had
some experience with them.

First of all, I have run flybacks directly off the tv/ computer circuit.  I
simply disconnected the high voltage "cup" from the CRT, made sure it didn't
arc to ground, and was able to sustain the voltage for an indefinite period.
Of course, as you say, you don't want to have to carry around the complete
monitor.

There are many circuits on the web for building portable driver circuits to
power flybacks, and with the right flyback and input voltages, up to 30 KV
output is possible.  One of the most common drivers used is found here:

  http://members.misty.com/don/samflyhv.html

I have built this circuit and used it myself.  It's ok, but if you want the
transistors to last any amount of time, a rather large heatsink is
necessary- I use something like a 4"x10" finned aluminum size.

There are better, nearly burnout proof circuits around the web, somewhat
more complicated than the above.  One example is here under "Efficient
driver circuit":

 http://www.kronjaeger.com/hv/hv/src/fly/index.html

Of course, this one is more complicated.  I haven't tried it myself.

Finally, there was an article that appeared in Aug. 1997 Electronics Now
magazine.  This featured an oil immersed modified flyback that provided 12
KV out at a generous amount of current (quite a lot more than normal because
of the modifications and being immersed).

One thing I've read over and over again is to make sure and use a discharge
resistor if arcing to ground, especially in the unprotected circuits.  This
can be a water filled hose or a chain of small resistors oil sealed into a
tube.  The purpose is to prevent internal, potentially destructive arcovers
within the flyback that would make it unusable.

Flybacks have a lot of potential.  They can be used for small Tesla coils or
even drive a voltage multiplier chain for very high ultimate voltages.  I
forget what you said your application was, but if you're looking at flybacks
you're probably heading in the right direction.

Hope this helps,
Jack