RE: [TCML] VTTC HP gate help Igbt?, was grid coil help

["Jim Mora" <wavetuner@xxxxxxxxx>]

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of futuret@xxxxxxx
Sent: Friday, July 03, 2009 6:01 PM
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] VTTC grig coil help

Hi Jim,

You mentioned the grid coil is 11" dia, but the primary is
8" dia.  Is this correct?  I would think they'd be about the
same diameter.

<snip>

No, sorry John, that is the height of the primary form. The primary and grid
coils are on it. I suspect it will be long enough. If the primary is at the
bottom, the height is about 5-6 inches. So the grid can slid away from the
primary. I can make it longer if needed by decommissioning  a spark gap demo
coil I made and fusing another 11" 8" acrylic form piece.
<snip>

I'm cogitating your well informed information. The voltage level = raw is no
problem if I can get the staccato to work somehow. Is there is another gate
type that can take that kind of power (2W) (not a triac clearly)? Much of
new power technology is new to me since I worked with signal transistors and
FET's and darlington power transistors. I suspect the silicon is out there
now for this application.

To get the grid type staccato to work, does the tube need to be biased in
the middle of the family of curves then driven into cutoff?

Maybe I need to learn about IGBT's sooner then expected. Someone that has an
idea please jump in. All we are doing is trying to turn the cathode on and
off to ground to vary the duty cycle of conduction to control the heat on
the tube's plate and change the spark output profiles. The current per tube
may be 550ma with an 833C and the floating voltage is 4-5.6KV which is
clamped to ground for conduction. So we are saturating a switch and then
removing the signal for the off time (cathode opened to ground). FYI a SCR
once triggered in the classic setup can't be shut off with a fullwave,
filtered power supply.

The staccato is positive leading for on time (saturation) I believe, and
goes low for cutoff. The signal level is out of a 555 pin 3 and probably
will need to be tweaked. How about it power folks, there should be a simple
thus elegant solution to this. 

Thanks Much,
Jim Mora


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