With CM300s or CM600s you can just double the 220 VAC line to get
642 VDC
for a good match.
If running, perhaps, a CM2400, you want to go up to near 2,400 VDC
on the
drive, so you end up using a 220/480 Volt 3 phase to get up to at or
near
the 2,400 VDC rectified. This gives you better output because you
go from
642 VDC to 2400 VDC that is being switched into the primary inductor.
Typically, with really large systems the only way to get from
220/440 VAC to
produce the 2400 VDC drive max is to use a small 25 to 50 kVA xmfr
(surplus
pole units).
Not a dual pole pig unit, just a 220/440 VAC 3 phase xmfr delivering
around
1650 VAC before rectification.
The main point with large DRSSTC type coils is efficiency ---
eliminating
all those losses in the heat & UV light production in the spark gap,
and
obtaining quicker dI/dt rates.
As you pointed out small and medium size coils run just fine without
using
any pole xmfrs. Usually above 15-18 ft long sparks the pole xmfr
boost
helps out get to the higher potential of the larger IGBTs without
wasting a
lot of headroom.
Dr. Resonance
On Sun, Jul 11, 2010 at 2:14 PM, Gary Lau <glau1024@xxxxxxxxx> wrote:
I'm going to bare my ignorance here. I thought that the whole
point of
solid state TC's was that you don't need a multi-kilovolt power
supply.
Are
pole pigs really used to power these? A _dual_ pig powered
magnifier???
Regards, Gary Lau
MA, USA
On Sun, Jul 11, 2010 at 12:16 PM, Scott Bogard <sdbogard@xxxxxxxxx>
wrote:
Hi John,
By chance is there a compiled list somewhere of "good IGBTs"
that
are used and those that aren't. Anyway back to the original
question, is
it
possible to parallel them? Lets say for kicks I'm building a dual
pig
powered 30kVa magnifier with a LTR cap (I'm clearly not, we are
talking
theoretical here.) Clearly the peak currents will be beyond any
reasonably
priced IGBT, is it possible to parallel lesser current units to
handle
the
load, and what would that entail? Thanks.
Scott Bogard.
On 7/10/2010 5:09 PM, John Forcina wrote:
Those IGBT's seem far from ideal. The TO220 package is a very poor
choice
as far as thermal conductivity and the datasheet says it all
0.75C/W.
You
will not be able to remove enough heat from the surface of the
IGBT die
quick enough between current pulses and the device will fail.
They do
not
have a internal anti-parallel diode so adding that externally
will add
to
the final cost also. Not to mention doing that will add
additional loop
area and stray inductance between units. One more thing is the
switching
times are surprisingly slow for that small of a unit. td(OFF)
96ns.
It's
not that slow however it does seem slow for that small of a
device. I
have
seen much better overall performance from larger IGBT's. My
suggestion
is
to just spend more money and use IGBT's that have been used and
proven
to
work in Tesla Coils time and time again. There must be some
reason that
we
all use them ;)
On Sat, Jul 10, 2010 at 4:38 PM, Scott Bogard<sdbogard@xxxxxxxxx>
wrote:
Interesting,
I am in the wee beginning stages of building my first
SISG, and
as
such am in the market for IGBTs. I found these, which look very
inexpensive
and have decent ratings.
http://www.newark.com/fairchild-semiconductor/hgtp12n60a4/single-igbt-600v-54a/dp/90B5642
My thinking is if heat is a problem or peak current, can I just
parallel
them? at $1.50 a pop it seems infinitely better than 1 $18 IGBT
of
nearly
the same ratings... I didn't look at temperature or package
information
yet, so maybe there is a problem there.
Scott Bogard.
On 7/10/2010 8:26 AM, McCauley, Daniel H wrote:
Scott,
The electric ratings may be the same or similar, but you also
have to
compare the mechanical ratings - in particular the thermal
ratings.
This
would be junction-to-case thermal impedances etc... The
expensive
IGBTs
that are commonly used in DRSSTCs are usually ISOBLOC type
packages
which
excellent thermal impedances. Compare this vs. a TO-247
package of
the
same
die.
And when comparing a TO-247 package to an ISOBLOC, keep in mind
that
you
STILL NEED to add a thermal insulator between the TO-247 and
heatsink,
which
just makes the thermal impedance even worse. The ISOBLOC (or
SOT-227)
doesn't require a thermal interface other a small smidgeon of
thermal
grease
or a graphite pad.
Dan
http://www.easternvoltageresearch.com
DRSSTC, SSTC, Flyback, Plasma Speaker Kits
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-
bounces@xxxxxxxxxx] On
Behalf Of Scott Bogard
Sent: Friday, July 09, 2010 9:52 PM
To: Tesla Coil Mailing List
Subject: EXTERNAL: [TCML] IGBT paralleling
Greetings all,
So, after a bit of researching I've noticed there are
IGBTs on
Newark with exactly the same ratings as some of the SSTC approved
IGBTs,
but
at 1/10th the price. What makes these others so special that
they are
better, and if it is just a matter of peak current ratings, since
IGBTs
are
gate driven, can we just parallel a few to get the required pulse
current
rating? I ask because I've not heard of anybody doing this, then
again
I've
only begun to research SSTC a little bit ago. Just musing.
Scott Bogard.
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla