Terry's DRSSTC - Stuff

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Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

Just to update.

I have been thinking about how to "stuff" everything into the chassis:

www.drsstc.com

If all goes well, only the MMC (just seven Geek style 150nF 2000V caps) and 
the coil itself will be external to the cabinet.  I think I can stuff 
everything else inside for a neat little box.  The box is also all black 
inside so the blown IGBT guts will not leave as visible marks :o))  The box 
looks a little small in the picture but it is 17 inches across and the 
white Delrin connector is 7.5 inches wide with 3/8 inch brass bolts and 
wing nuts.  I'll just mill through the paint on the 1/8 inch aluminium side 
panels for the bridge and resistor heat sinking. The side panels can also 
hole the power supply and input filter nicely out of the way.

I added the power supply and a ground neutral fault detect (LED and 
resistor ;-)) circuit to the input section:

http://drsstc.com/Design/InputSection.gif

The fan moved on the other side of the breaker so it will always be on to 
blow out the smoke ;o)

In the case of a miss-wired AC receptacle, a red LED will warn before 
popping the breaker.  Since I am shorting neutral and the AC ground, if the 
receptacle is wired wrong I would be shorting ground and AC hot.  The LED 
would warn of that.  The breaker would just pop in any case but it might 
reduce the drama.

I simplified the protection circuits to 3 ICs and one PC board yet to be 
laid out:

http://drsstc.com/Design/ProtectionCircuit.gif

The center tapped CT was good for getting rid of the negative side current 
detection circuit stuff.  One "could" just sense on positive but things can 
bite you...  With the center tapped CT you can see both negative and 
positive over current events.  The LM339 is slow, but good enough here. 
That is a great CT!  DigiKey # 237-1097-ND plus a 1 ohm resistor gives a 
great 10kHz to 200kHz 100:1 current output signal for $7.00!:

http://drsstc.com/Design/CurrentTransformerTest.pdf

I think I finally have just about all the parts but just need to work on 
getting it together now ;-)  I should mention that NONE of this has been 
actually tested yet and I will have to work out any unforeseen 
problems.  However, this stuff is in the "normal" world of circuit design, 
so they "should" be easy to fix.

Total cost is coming in at about $1500 for a no hold bars amateur R&D 
project.  About 1/500th the cost of doing it at the day job ;-)  But my 
labor is free and I don't have a board of directors telling me how to cut 
costs :o)))  With a few safety covers, it might even make CE and TUV for 
the base unit, but that is not a concern to me.  Even though it may seem 
expensive, take away all my "decadent fancy stuff" and the base electronics 
is really dirt cheap!!  My IGBTs cost $5.33 each in QTY/100, but a lot of 
other types should work fine too.  Lots of time goes into the documentation 
and the web page!  But unlike the OLTC, you "know" what I am up to ;-))

This is all great fun!!  Spending lots of money, getting lots of cool 
parts, and playing with all my cool toys ;-)))  Things will slow here at 
the holidays even though I tried to 2-day in a bunch of stuff before 
Christmas ;-))  I am very hard at it here!!

Cheers,

	Terry