Hi Bart,
Maybe the prices went up due to commodity prices which may still have
been soaring
a year ago. But still the price increase seems extreme, but then
again I have no
idea how they determine prices on these things. I remember seeing
some postings
about the die size and all recently, I guess those were yours. Well
I'll be looking
forward to your ongoing results. I guess you'll be posting pictures
and full specs
eventually (or maybe I missed them). Maybe eventually as these type
of IGBT's
are used in more commercial products maybe it will be possible to find
them in
scrapyards and flea markets, etc, inside certain equipment.
I'm working on a very small simple VTTC at the moment which is
actually some
progress for me since I haven't been doing much TC work lately. Your
JavaTC
is coming in handy for the VTTC.
Cheers,
John
-----Original Message-----
From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sun, 19 Oct 2008 8:46 pm
Subject: Re: [TCML] SISG First Light
Hi John,
Originally, I think they were in the $8 range. But 1 year later, they
were over $20 each and hard to come by and as time progressed, they
were closer to $30ea. When I bought Marks boards, I decided to pick up
the components myself. I waited for a time to see if prices would drop
down (it didn't). I think Mark picked up a batch
later on for a decent bulk price and was able to sell them at a very
low cost ($10 each or something like that) and had offered to sell me
some at that price. I declined the offer only because I couldn't
afford the expense at the time (without my wife killing me). So I
waited. Then I got tired of waiting and started looking for an
alternative. That's when I came across the Fairchild IGBT's. The specs
were close enough to be a drop in replacement and it was only the
power dissipation which I worried about.
When Terry picked the IGBT for his SISG, he went with the best out
there at the time and the price back then was doable. The main
difference is the die size which dictates thermal dissipation. My
IGBT's have a smaller die size and will run warmer, but if they have
ample heat sinking and air, then it's manageable. After the run, I put
my hand down by the air exit hole in the cabinet (with the fan still
blowing) and the air was only a slight temp difference, but barely
noticeable.
Of course, I'm just starting out. If I double up on the current, maybe
then I'll see an issue or at least a noticeable change in temp. I
think I'll bring home a temp probe and attach it to one of the IGBT's
and measure how hot it actually gets. This was a long continuous run,
so the IGBT's had plenty of time to heat up to the maximum allowable
temp under the conditions and stabilized (which I think was relatively
cool).
Take care,
Bart
futuret@xxxxxxx wrote:
Hi Bart,
That all sounds wonderful, definitely so. It is truly a marvelous >
invention by Terry.
What is the main differences with this new IGBT as compared to the >
previous
type, the type that Mark Dunn was selling for a time?. I guess the >
peak current
rating is a little lower, but the price is much lower? Is that about
the extent
of it? I seem to remember the other IGBT's were about $10 each?
John
-----Original Message-----
From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sun, 19 Oct 2008 6:19 pm
Subject: Re: [TCML] SISG First Light
Hi John, > > I just finished installing the 6th SISG board and
running the system. > I have k low at 0.112 (meas.). I'm running low
Cp at a measured 65nF. > I just came in from a 10 minute duration run
with the coil. It ran > flawlessly throwing out 5 foot free air
streamers at 200V/11A input. > It looks like (in my case anyway), your
spark length equation holds > well for my SISG coil. During the run, I
ran at higher and lower > voltages and compensated with current. In
both cases, it didn't make > much of a difference (I20could do about
the same with both extremes). > One thing I noticed is when I increase
power, pps would increase and > there is a spot where your just on the
edge of the coil running a nice > 120 bps (as well as my ears could
detect), but when I threw more power > at it, the coil began to sound
odd. I could tell the sisg was not > firing smoothly. Kind of a DRSSTC
sound to the sparks. So I kept it at > that edge of running smoothly
and just let it run. > > I did have a fan blowing inside the chamber.
I'm using a Fairchild > IGBT on the boards (HGTG18N120B). Mouser has
them for $5.30ea in > quantities of 1. Mouser has 283 in stock and
nearly 10,000 showing up > in a few days, so these IGBT's are probably
the way to go with the > SISG boards (IMHO). They probably run a
little hotter, but with air > cooling, that's no big deal. Here's the
data sheet. > http://www.fairchildsemi.com/ds/HG/HGTG18N120BND.pdf > >
Anyway, a great continuous 10 minute run and no problems at all. I >
think I see why large Cp would be best for an SISG. Had I double the >
tank C, I could have doubled the current at the pps where the IGBT was
> happy. But as far as running ability with a low Cp, there are no >
problems that I can detect. So an SISG can be a direct replacement for
> a conventional spark gap. > > I'm happy with my SISG coil. I
designed it for no primary tuning
(ribbon), so I'm using the full turns. All I
did was raise the toroid > 2 inches. I measured within 1kHz of the
calculated value, so it all > worked out as planned. > > I should note
I am still using a breakout point. It did breakout of > the 9" x 30"
toroid with the 6th board, but it=2
0was not consistent. > > Another very important point to note. After
my 10 minute run, I went > and asked my wife about static on the TV.
There was "NONE" she said! > What an improvement! Might make the
"perfect" spark gap replacement > for those who live in apartments. >
> So kudo's to Terry Fritz for inventing the SISG and to Mark Dunn and
> others who took the SISG to new levels. > > Cheers, > Bart > >
futuret@xxxxxxx wrote: >> Bart, >> >> Congratulations on your initial
results. I have the SISG boards and > > IGBT's >> but have not done
anything further yet. >> >> John >
_______________________________________________ > Tesla mailing list >
Tesla@xxxxxxxxxxxxxx > http://www.pupman.com/mailman/listinfo/tesla >
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