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SISG Update

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Terry Fritz

Wed Jul 26 2006, 02:27AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi,

I have been real busy with the SISG

)

I "originally" started out to make a "little" solid state disruptive coil for research use. Done now!!!

)

It is perfect

))) Never changes, always there, runs perfectly consistent!!! Prolly lasts forever too!! Very precise parameters!!!

But being a "little friendly coil", is is not a big sparker... Can only jump a foot... Don't want to fry the $4000 scope and stuff...

So I guess we need a "bigger" sparker >:D

Preliminary plans are here:

A single MOT coil about 18 inches high that should do 30 inch sparks. It uses a new DC MOT charging circuit that seems cool so far:

The file is out of date in that the AC inductor is useless...

The system should scale right up!!! Like to four MOTs >:-))) The resistors cooking off power is a pain. Steve Conner is working that along with triggering

)

I have determined that simply varying R4 will never get to first notch quenching. The voltage drop on the gate is too slow (e^(-t/RC)) and the currents needed over time or too high for the curve. No chance at all... So that will take "more"... Not much power in the gate so a 2N2222 could drop it like a rock...

Interesting that the high primary "Q" of the SISGs low loss is now being put to giant primary cap values

Primary RMS current is pretty high too!! I just stuffed in primary capacitance for power at the expense of Q figuring that everything happens "soon in the function"... That is a good formula proven over decades

)

I fiddled some with a new SISG board. But the costs were high and Mark Dunn's boards are super fine:-))

Best to save the trouble and cash for more important stuff now... Like IGBTS in bulk

) Get the leaded versions for 1/2 price!!!!

So that is what I know.... Parts coming in this week... "Nice" source for "new" microwave parts here

))

(put mouse over "by Part" for lists)

I just got my stuff from them and very fast too!!! Screw E-bay

)

Cheers,

Terry

ragnar

Wed Jul 26 2006, 03:23AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Ooo, Terry, this feels big!

Where are you getting your boards made, again?

Marko

Wed Jul 26 2006, 12:57PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

One thing I wondered; are there any hopes actually for better quenching with SISG?
It does compensate somewhat with it's low-loss, and making all IGBT's close rapidly after first notch and keeping relative simplicity of the system (no external power and etc.) seems quite hard

PS. I've been in trouble seeing most of terry's papers, I managed to open one pdf after ages of loading, sometimes I simply time out. ANyone else got the same problem?
SOmetimes it works, sometimes it simply won't load...

And needles to say, coil looks great from what I've seen. I like the big spun toroid on a little coil

HV Enthusiast

Wed Jul 26 2006, 04:47PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Looking good Terry - can't wait to see the finished result!

dan

Wed Jul 26 2006, 06:30PM

Registered Member #223 Joined: Mon Feb 20 2006, 06:42PM
Location: Ottawa, Ontario, Canada
Posts: 125

Yes good work Terry. You are truly an asset to the coiling community.

I hope to be as awe inspiring as you one of these days

As for the pdf I too have had trouble loading them. Adobe reader is really bloated for what it does. It takes forever to load on my crappy but still decent computer.

Terry Fritz

Wed Jul 26 2006, 10:09PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Where are you getting your boards made, again?

ExpressPCB

They give you nice free schematic and board layout software. They have a bunch of service types from a few prototypes for a great price to full production stuff.

One thing I wondered; are there any hopes actually for better quenching with SISG?

It would probably take some type of little electronic timer powered from the voltage on C1. Like a small SCR (2N5062) that could be fired at some special time to drain the gate and all... There is one big advantage to quenching on the SISG, it cuts down on the IGBT heating. It is not much now, but the heatsinks could be super small if the RMS currents from the notches was removed. Perhaps C1 could be larger and R4 removed. Then another RC could raise the votlage on the SCR trigger. Mayb a FET with an RC delay could do it too.

Update: Maybe something like this:

Just an added cap and little T0-92 SCR. The cap should be NPO for temperature stability. I worry about the trigger voltage drifting with temperature on the SCR, but at moderate BPS the power in the SCR is nil. My coil would like to quench at 22uS so about a 600 ohm resistor.

I've been in trouble seeing most of terry's papers

It's a DSL connected server here on my desk. Try again latter or try "save as". It is usually fine unless there is other stuff clogging the pipe.

Cheers,

Terry

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