DRSSTC Thoughts
Updated/Edited: October 23, 2004
First Post
Subject: DRSSTC thoughts...Date: Tue, 28 Sep 2004 17:24:03 -0600
Original poster: Terry Fritz.
Hi All, I have not been following the DRSSTC things much. Been very
busy for about the last year... But after reading Dan's new book I have
some questions/comments.
Dan – I see you used the model for streamer loading of 220K + 1pF/foot for a
streamer load in your SPICE models. I was just wondering how well that
worked for you? There is some concern that model is just “too simple” for
some things, so I was curious if it worked well in this case?
I also note from Dan's book that he has “almost” as many “toys” as "I" do!! :o))
I see that super high current IGBT's are really in demand now ;-)) But
monsters like the fabulous Powerex CM600HA-24H my be too heavily designed for
“power” when what we need is “current”. It can “officially” do 1200 amps
peak which is nice but I know we don't need the 4200 watts of power dissipation
;-)) So I wish to remind of the simple IR IRG4PH50UD. A lowly 24 amp
rated TO247AC IGBT with diode. But it uses a great big die in a small
package thus it's 180 Amp peak rating ;-)) Note that some people have put
a lot more current through them like this one happily eating 700+ amps :o))
http://hot-streamer-dot-com/temp/OLTC08-30-02.gif
http://hot-streamer-dot-com/temp/OLTC08-30-01.jpg
Above about 740 amps, the signal starts “flat topping” do to the fact that the
gate structure simply cannot support more current no matter how high the gate
voltage is. BTW – I note a lot of folks no longer worry much about the
maximum gate voltage specs :o))
Using big IGBT's might not be a problem if you can get them cheap. Mouser
has them for only $330 (new which is a great price!!) But suppose we just
can't find them “cheap” or want new IGBTs without spending $1300... Then
using a few of the little IRG4PH50UD IGBTs may start to be a good deal.
They cost $16 a “pop”. If you get $1300 worth of them, you have 20 IGBTs
per leg at 3600 amps peak “rated” and 14000 amps “unrated”!! So it may be
useful to consider a “multi-mini IGBT” (MMIGBT ;-)) array in some cases.
Of course, we don't need 80 of them. But maybe 12 would do for about $200.
Everything from the drive circuits back is just the same as usual... One
can typically find the peak current using straight forward calculations.
However, Dan's data shows the primary current can almost double during a ground
strike!! That is a critical bit of info!! Do the models show that
behavior too?
Of course, if off the self IGBTs just are not right, check this DigiKey part out
;-))
IRG4CC50UB-ND
600V 55A for a buck ;-)) I bet you can find a wire bonder on E-bay for a
song (Yipps!! guess not
(http://cgi.ebay-dot-com/ws/eBayISAPI.dll?ViewItem&category=45045&item=3842974611)...
Just use the silver epoxy for the pad bonding too...)... Silver filled
epoxy for mounting, and your there baby!! :o)))
Also note that the primary cap strings could be distributed between the IGBTs to
force current sharing like the OLTC does if that would help:
http://hot-streamer-dot-com/temp/OLTC8-10-01.gif
http://hot-streamer-dot-com/temp/OLTC8-10-02.gif
For driving IGBTs, don't forget the wonderful TLP250:
http://rocky.digikey-dot-com/WebLib/Toshiba/Web%20Data/TLP250.pdf
Too bad it probably does not have enough frequency in this case. But it's
real claim to fame was that it was optically coupled to give 2500 volts of
insulation which could eliminate the drive transformer!! =:O One can
play little zener/resistor/cap tricks from emitter to collector to find the
power to run the hot side. Hopefully, there may be a faster version
lurking out there somewhere now.
Apparently, primary to secondary arcing is a problem. This is often
due to incorrect primary to secondary tuning. Since DRSSTCs are self
tuning, there may need to be a little “tweaking” the that circuit to better
match/lock the primary and secondary frequencies.
Dan states that “protection” circuits could use some work... They will
probably be pretty simple and easy. “Figuring them out” is the hard part
;-)) Transorbs and MOVs can do wonders!!
The SPICE models can be used to force all kinds of fun fault conditions too.
Primary to secondary arcs and such are just t timed switch away. These
studies tend to reassure one that such events usually are not too bad and can
also find a few real doozies!
One may “possibly” be able to use 60Hz resonant primary charging for the DRSSTC
like the OLTC used. That would eliminate a lot of the DC charging and
giant cap stuff. But I do note that “I” seem to be the only one foolish to
go that way ;-)) But I have not had any problems with it...
It would be neat if there were a fairly off-the-shelf system that could be
hooked up to any already made coil to get rid of the HV stuff and simply convert
it to DRSSTC operation right then and there. I know a number of people
have boards out now so maybe I am just all behind times ;-))
So it looks like the old NST class systems have a giant competitor now...
I thought the OLTC would do it, but that system runs into some issues that make
it rather difficult. Of course, Steve Conner took it to the MAX!!
Sorry I never go a nice write up for it done... I am happy to see a few of
it's tricks made it into the DRSSTC, but I think a few tricks may have gotten
missed too ;-)) I too must think that the days of the spark gap coil are
numbered. Not because there “are” good SSTCs out there, but because the
will soon simply be the “best” TCs... Even “big” systems are coming to
speed fast!! The record for a point to point arc is 59 feet...
Maybe this all will be a bit of help, forget any parts that are obviously stupid
:o)). Cheers, Terry.
Date : Tue, 28 Sep 2004 21:13:15 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Steve Ward"
<steve.ward@gmail.com>
Hey Terry, Some comments:
> Dan I see you used the model for streamer loading of 220K + 1pF/foot for
> a streamer load in your SPICE models. I was just wondering how well that
> worked for you? There is some concern that model is just "too simple" for
> some things, so I was curious if it worked well in this case?
Steve Conner has been battling this one for a long time. A real streamer model
is the #1 hindrance in simulations i feel. Its just hard to get it exact. And
your results can change wildly depending on what you used for a streamer
model! Am i gonna see 1000A or 2500A? was my question at one time :-P.
> I see that super high current IGBTs are really in demand now ;-)) But
> monsters like the fabulous Powerex CM600HA-24H my be too heavily designed
> for "power" when what we need is "current". It can "officially" do 1200
> amps peak which is nice but I know we don't need the 4200 watts of power
> dissipation ;-))
Yeah exactly. They also didn’t strive to minimize stray L inside the bricks
either. Greg Leyh wrote an article on this... cant remember where to find it
though. As we push these IGBT’s harder and harder the little things like stray
L inside the IGBT will add up quick! And heck, we'd be doing something bad if
we dissipated over 50W per IGBT (unless it was a REALLY big system). Even with
making 11 footers, my IGBTs stay cold to the touch.
So I wish to remind of the simple IR IRG4PH50UD. A lowly
> 24 amp rated TO247AC IGBT with diode. But it uses a great big die in a
> small package thus it's 180 Amp peak rating ;-))
Yeah, that's a tough little guy!
Note that some people
> have put a lot more current through them like this one happily eating 700+
> amps :o))
>
If only the bigger IGBTs could withstand such abuse. I only run my CM300s at 2X
their peak rating.
>
> Above about 740 amps, the signal starts "flat topping" do to the fact that
> the gate structure simply cannot support more current no matter how high
> the gate voltage is. BTW I note a lot of folks no longer worry much
> about the maximum gate voltage specs :o))
Seems that 30V or so is common now, at least thats what i always use.
But suppose we just
> can't find them "cheap" or want new IGBTs without spending $1300... Then
> using a few of the little IRG4PH50UD IGBTs may start to be a good
> deal. They cost $16 a "pop". If you get $1300 worth of them, you have 20
> IGBTs per leg at 3600 amps peak "rated" and 14000 amps "unrated"!! So it
> may be useful to consider a "multi-mini IGBT" (MMIGBT ;-)) array in some cases.
Yeah, that certianly is impressive. And it seems that you could take more
control of problems with stray L. Then again, how to minimize inductance on a
layout consisting of so many individual devices is quite a feat!
However, Dan's data shows the primary current can almost
> double during a ground strike!! That is a critical bit of info!! Do the models show that behavior too?
Ive simulated this in some of my models. My big coil has active current
limiting to keep things "safe" under these conditions. Shorter, heavier arcs
make things much worse as they present lower impedances.
>
> Of course, if off the self IGBTs just are not right, check this DigiKey part out ;-))
>
> IRG4CC50UB-ND
>
> 600V 55A for a buck ;-)) I bet you can find a wire bonder on E-bay for a song (Yipps!! guess not
>
(http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=45045&item=3842974611)...
> Just use the silver epoxy for the pad bonding too...)... Silver filled epoxy for mounting, and your there baby!! :o)))
Oooh, now THAT can get interesting. Talking to Jimmy Hynes, the idea came up to
make our own bricks with some dies, but instead of designing for lots of power,
design it to withstand very high temperature transients. That is, put heatsinking on BOTH sides of the die to remove heat even faster. Or even just
some sort of small aluminum block on top of the dies to wick away heat faster...
then IT can be dealt with via forced air cooling. I wonder if they come in
1200V versions :-).
> Also note that the primary cap strings could be distributed between the
> IGBTs to force current sharing like the OLTC does if that would help:
Not sure if there would be much reason for that one, though if we were
paralleling a bunch of small IGBTs it may somehow work.
> Apparently, primary to secondary arcing is a problem. This is often due to
incorrect primary to secondary >tuning.
Or your secondary throwing sparks 3X its length! Thats when my coil starts to
show some signs of being stressed out ;-)
Since DRSSTCs are self tuning,
> there may need to be a little "tweaking" the that circuit to better match/lock
the primary and secondary >frequencies.
Well, the tank circuit cant tune itself. I think that is what was
meant. Tweaking the primary L is what is needed... or just turn down the variac
a bit ;)
>
> The SPICE models can be used to force all kinds of fun fault conditions
> too. Primary to secondary arcs and such are just t timed switch
> away. These studies tend to reassure one that such events usually are not
> too bad and can also find a few real doozies!
Ooh, i will have to try that out in my next sim.
>
> One may "possibly" be able to use 60Hz resonant primary charging for the
> DRSSTC like the OLTC used. That would eliminate a lot of the DC charging
> and giant cap stuff. But I do note that "I" seem to be the only one
> foolish to go that way ;-)) But I have not had any problems with it...
I don't think *my* line can supply 1200A for even very short periods of time. I
think we need these big DC caps there to be a low Z power supply. Maybe I’m
wrong.
>
> It would be neat if there were a fairly off-the-shelf system that could be
> hooked up to any already made coil to get rid of the HV stuff and simply
> convert it to DRSSTC operation right then and there.
The main problems are 1) tank impedance for DRSSTCs are usually less than that
of a SGTC. 2) operating frequencies can tend to be too high for efficient use
of a solid state driver using slugish IGBTs (though they are indeed getting much
faster!).
I too must think that the days of the
> spark gap coil are numbered. Not because there "are" good SSTCs out there,
> but because the will soon simply be the "best" TCs... Even "big" systems
> are coming to speed fast!! The record for a point to point arc is 59 feet...
59' for what??? a solid state system? I was pretty sure that SGTCs were beyond
those spark lengths for some of the larger systems, but maybe not? Steve.
>
> Maybe this all will be a bit of help, forget any parts that are obviously stupid :o)).
Cheers, Terry.
Date : Tue, 28 Sep 2004 21:45:05 -0600. Subject : Re: DRSSTC thoughts...
Original poster: Terry Fritz
<teslalist@twfpowerelectronics.com>
Hi Steve,
At 09:03 PM 9/28/2004, you wrote:
>Hey Terry,
>
>Some comments:
>
> >
> > Dan I see you used the model for streamer loading of 220K + 1pF/foot for
> > a streamer load in your SPICE models. I was just wondering how well that
> > worked for you? There is some concern that model is just "too simple" for
> > some things, so I was curious if it worked well in this case?
>
>Steve Conner has been battling this one for a long time. A real
>streamer model is the #1 hinderance in simulations i feel. Its just
>hard to get it exact. And your results can change wildly depending on
>what you used for a streamer model! Am i gonna see 1000A or 2500A?..
>was my question at one time :-P.
I guess it is the "best guess " out there.... Any info on the "troubles" would
be useful to go to the "next step"...
> > I see that super high current IGBTs are really in demand now ;-)) But
> > monsters like the fabulous Powerex CM600HA-24H my be too heavily designed
> > for "power" when what we need is "current". It can "officially" do 1200
> > amps peak which is nice but I know we don't need the 4200 watts of power
> > dissipation ;-))
>
>Yeah exactly. They also didnt strive to minimize stray L inside the
>bricks either. Greg Leyh wrote an article on this... cant remember
>where to find it though. As we push these IGBTs harder and harder the
>little things like stray L inside the IGBT will add up quick! And
>heck, we'd be doing something bad if we dissipated over 50W per IGBT
>(unless it was a REALLY big system). Even with making 11 footers, my
>IGBTs stay cold to the touch.
Stray emitter inductances and higher frequencies and giant currents can far
exceed our gate drive voltages... Thus, the "Kelvin" connections.... The big
boy makers will "feel our pain" here and make them for us ;-)))
> So I wish to remind of the simple IR IRG4PH50UD. A lowly
> > 24 amp rated TO247AC IGBT with diode. But it uses a great big die in a
> > small package thus it's 180 Amp peak rating ;-))
>
>Yeah, thats a tough little guy!
>
> Note that some people
> > have put a lot more current through them like this one happily eating 700+ amps :o))
> >
>
>If only the bigger IGBTs could withstand such abuse. I only run my
>CM300s at 2X their peak rating.
>
> >
> > Above about 740 amps, the signal starts "flat topping" do to the fact that
> > the gate structure simply cannot support more current no matter how high
> > the gate voltage is. BTW I note a lot of folks no longer worry much
> > about the maximum gate voltage specs :o))
>
>Seems that 30V or so is common now, at least thats what i always use.
50V is the "killer" there.... But above 30V does no addled good...
> But suppose we just
> > can't find them "cheap" or want new IGBTs without spending $1300... Then
> > using a few of the little IRG4PH50UD IGBTs may start to be a good
> > deal. They cost $16 a "pop". If you get $1300 worth of them, you have 20
> > IGBTs per leg at 3600 amps peak "rated" and 14000 amps "unrated"!! So it
> > may be useful to consider a "multi-mini IGBT" (MMIGBT ;-)) array in some cases.
>
>Yeah, that certianly is impressive. And it seems that you could take
>more control of problems with stray L. Then again, how to minimize
>inductance on a layout consisting of so many individual devices is quite a feat!
Most BIG IGBTs are a "bungled mess" when it comes to higher frequencies...
> However, Dan's data shows the primary current can almost
> > double during a ground strike!! That is a critical bit of info!! Do the models show that behavior too?
>
>Ive simulated this in some of my models. My big coil has active
>current limiting to keep things "safe" under these conditions.
>Shorter, heavier arcs make things much worse as they present lower impedances.
Cool!!! We will prepare for that!!!!
> >
> > Of course, if off the self IGBTs just are not right, check this DigiKey part out ;-))
> >
> > IRG4CC50UB-ND
> >
> > 600V 55A for a buck ;-)) I bet you can find a wire bonder on E-bay for a song (Yipps!! guess not
> >
> (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=45045&item=3842974611)...
> > Just use the silver epoxy for the pad bonding too...)... Silver filled
> > epoxy for mounting, and your there baby!! :o)))
>
>Oooh, now THAT can get interesting. Talking to Jimmy Hynes, the idea
>came up to make our own bricks with some dies, but instead of
>designing for lots of power, design it to withstand very high
>temperature transients. That is, put heatsinking on BOTH sides of the
>die to remove heat even faster. Or even just some sort of small
>aluminum block on top of the dies to wick away heat faster... then IT
>can be dealt with via forced air cooling. I wonder if they come in 1200V versions :-).
"Top of die" heat sinking is typically a "giant" disaster in the
industry... Cray tried it but.... Disaster... Best to use old "thin die"
bottom thermal dissipation teck there... Happily, within reach of "basement
shops" these days ;-)))
> >
> > Also note that the primary cap strings could be distributed between the
> > IGBTs to force current sharing like the OLTC does if that would help:
>
>Not sure if there would be much reason for that one, though if we were
>paralleling a bunch of small IGBTs it may somehow work.
It was a "giant deal" for the OLTC... Maybe not a big deal in the "end game"...
> > Apparently, primary to secondary arcing is a problem. This is often due
> > to incorrect primary to secondary tuning.
>
>Or your secondary throwing sparks 3X its length! Thats when my coil
>starts to show some signs of being stressed out ;-)
Jimmy had computerized circuits there ;-))) Can we say "predictive impedance
compensations" and such ;-)))
> Since DRSSTCs are self tuning,
> > there may need to be a little "tweaking" the that circuit to better
> > match/lock the primary and secondary frequencies.
>
>Well, the tank circuit can't tune itself. I think that is what was meant. Tweaking the primary L is what is
>needed... or just turn down the variac a bit ;)
Yep!! Need to thinkies there...
> >
> > The SPICE models can be used to force all kinds of fun fault conditions
> > too. Primary to secondary arcs and such are just t timed switch
> > away. These studies tend to reassure one that such events usually are not
> > too bad and can also find a few real doozies!
>
>Ooh, i will have to try that out in my next sim.
";-)))) Yaeh!!! Tell the model to predict what happens when things go all
wrong...
> >
> > One may "possibly" be able to use 60Hz resonant primary charging for the
> > DRSSTC like the OLTC used. That would eliminate a lot of the DC charging
> > and giant cap stuff. But I do note that "I" seem to be the only one
> > foolish to go that way ;-)) But I have not had any problems with it...
>
>I dont think *my* line can supply 1200A for even very short periods of
>time. I think we need these big DC caps there to be a low Z power supply. MaybeI’mwrong...
An interesting area there... Big inverters draw giant currents for tiny bits of
time off the AC line and seem to "get away with it" very well...
> >
> > It would be neat if there were a fairly off-the-shelf system that could be
> > hooked up to any already made coil to get rid of the HV stuff and simply
> > convert it to DRSSTC operation right then and there.
>
>The main problems are 1) tank impedance for DRSSTCs are usually less
>than that of a SGTC. 2) operating frequencies can tend to be too high
>for efficient use of a solid state driver using slugish IGBTs (though they are indeed getting much faster!).
>
>I too must think that the days of the
> > spark gap coil are numbered. Not because there "are" good SSTCs out there,
> > but because the will soon simply be the "best" TCs... Even "big" systems
> > are coming to speed fast!! The record for a point to point arc is 59 feet...
>
>59' for what??? a solid state system? I was pretty sure that SGTCs
>were beyond those spark lengths for some of the larger systems, but maybe not?
That was 59 "FEET" ;-))) Ain't NO solid state system gotten that far :o))))
Cheers, Terry.
>Steve
> > Maybe this all will be a bit of help, forget any parts that are obviously stupid :o)). Cheers, Terry.
Date : Tue, 28 Sep 2004 21:47:02 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Jim Lux"
<jimlux@earthlink.net>
> >
> > Dan I see you used the model for streamer loading of 220K + 1pF/foot
for
> > a streamer load in your SPICE models. I was just wondering how well
that
> > worked for you? There is some concern that model is just "too simple"
for
> > some things, so I was curious if it worked well in this case?
>
> Steve Conner has been battling this one for a long time. A real
> streamer model is the #1 hindrance in simulations i feel. Its just
> hard to get it exact. And your results can change wildly depending on
> what you used for a streamer model! Am i gonna see 1000A or 2500A?.. was my question at one time :-P.
>
And even harder to represent a streamer in spice...
Several ideas:
A series of transmission lines with very high impedances and slow propagation
constants.
Some sort of time sequenced switches.
The idea is to get a series of capacitors that gradually get added on the end
(which replicates the behavior of a leader progressing in short jumps).
Date : Tue, 28 Sep 2004 22:04:13 -0600. Subject : Re: DRSSTC thoughts...
Original poster: Terry Fritz
<teslalist@twfpowerelectronics.com>
Hi, The "record here" stands at a 59 foot arc from "point to point"... for
"any" "Tesla coil..." Bill Wysock's model 13...
http://www.ttr.com/model13.html
But the solid state folks ain't no pushovers when it come to giant switches!!!
http://accelconf.web.cern.ch/accelconf/l00/papers/WE103.pdf
Expect us to get kicked in the A** real soon there ;-))
But folks devoting such "big bucks" to "Tesla coils" is a limiter for
now... But the technology and brains are floating around out there now to blow
us all away ;-))).
Cheers, Terry.
Date : Tue, 28 Sep 2004 22:06:04 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Jim Lux"
<jimlux@earthlink.net>
> Yeah exactly. They also didnt strive to minimize stray L inside the
> bricks either. Greg Leyh wrote an article on this... cant remember
> where to find it though. As we push these IGBTs harder and harder the
> little things like stray L inside the IGBT will add up quick! And
> heck, we'd be doing something bad if we dissipated over 50W per IGBT
> (unless it was a REALLY big system). Even with making 11 footers, my
> IGBTs stay cold to the touch.
But guys (and gals), you're designing RF power amplifiers now.. maybe you
need to add some C to the system to cancel the reactance of the L. This is
the whole matching thing and, aside from "minor details" like thermal
management, it's what makes it a challenge (speaks someone whose office mate
just fried some DEI/Ixys kilowatt FETs). Not having looked into the design
problems, I can't say whether it's even feasible to match these devices in
that way, but dealing with package parasitics has been an aspect of power
amplifier design from the days of the first Audions.
> Yeah, that certianly is impressive. And it seems that you could take
> more control of problems with stray L. Then again, how to minimize
> inductance on a layout consisting of so many individual devices is quite a feat!
Do you actually need to minimize it, or can you go towards a "distributed
amp" kind of topology, using the parasitic L with appropriate networks to
make a transmission line. Don't switch them in parallel, but stagger the
gate signals and drain connections.
>
> Oooh, now THAT can get interesting. Talking to Jimmy Hynes, the idea
> came up to make our own bricks with some dies, but instead of
> designing for lots of power, design it to withstand very high
> temperature transients. That is, put heatsinking on BOTH sides of the
> die to remove heat even faster. Or even just some sort of small
> aluminum block on top of the dies to wick away heat faster... then IT
> can be dealt with via forced air cooling. I wonder if they come in 1200V versions :-).
Or consider other substrates to bond the die to (AlSiC or CVD diamond?).
Thermal management is going to be the key.
> >
> > Also note that the primary cap strings could be distributed between the
> > IGBTs to force current sharing like the OLTC does if that would help:
>
> Not sure if there would be much reason for that one, though if we were
> paralleling a bunch of small IGBTs it may somehow work.
If you're going for a distributed amp kind of architecture, then it's a natural
development. Think in terms of the stacked Blumlein pulse generators.
Date : Tue, 28 Sep 2004 22:06:28 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Jim Lux"
<jimlux@earthlink.net>
> Original poster: Terry Fritz
<teslalist@twfpowerelectronics.com>
> >I dont think *my* line can supply 1200A for even very short periods of
> >time. I think we need these big DC caps there to be a low Z power supply. Maybe im wrong...
>
> An interesting area there... Big inverters draw giant currents for tiny
> bits of time off the AC line and seem to "get away with it" very well...
>
big inverters use inductors and PWM input circuits, etc. to make the PF better.
Date : Tue, 28 Sep 2004 22:07:49 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Mike"
<induction@comcast.net>
Hi Terry, Steve and everyone. About the cooling issues, especially the die's,
and whole devices, I like water cooling. Distilled water of course and
non-conductive hose, ~1 foot
per kV in length and then some safety factor. At work we routinely use it
cooling the big triodes of induction heaters of 600 kW output class and also for
the "hockey puck" large SCR's controlling the 480 volt 3 phase to the
transformer primary. Leakage to ground is not a problem with good water, a
non-iron pump and heat exchanger. Even the solid state machines use water
cooling, be they the older "fast" SCR type or IGBT type. On the larger tube
machines at ~450 kHz and down (280 kHz typical on thermatool pipe welders) we
have no problem with water cooling 22,000 volts at 30 amp power supplies. It
does help to have a corona ring /cone the first foot from the water jacket
(anode) around the feed/drain hoses as they pull away from that water jacket to
the hose trap / coil wound to get enough feet before hitting the feed and drain
manifolds, otherwise that end(s) dielectric heat somewhat. But for that kind of
voltage DC and RF, this is not so hard to do and one ring protects both hoses.
For the power levels spoken of on the coils, a very modest pump and exchanger
would be very easy to do and is quiet. Even the CQK-650 tube, tetrode, is rated
at 22 kV, 100 amps anode (CW), 1.77 output Mw with 900 watts signal grid drive,
used on VOA is water cooled without problems. Our old tube re-building division
used to rebuild them and the smaller CQK-450. Point being water and electricity
do mix if done right. Regards, Mike.
Date : Tue, 28 Sep 2004 22:20:54 -0600. Subject : Re: DRSSTC thoughts...
Original poster: Terry Fritz
<teslalist@twfpowerelectronics.com>
Hi, "DI" water trends to "tear up" things... We have a 60KW generator here that
can waist 30kW into the dirty cooling water as a pure resistive VI... Water
cooling "can be" like 100X better!!! But be very careful of having voltages
across that water barrier... We have giant IGBTs with water directly on their
backs, but thermal studies suggest we need copper heat spreaders instead for max
dissipation... Big tubing lengths are legendary for fighting this... but that
gets silly after a point. Cheers, Terry.
Date : Tue, 28 Sep 2004 22:22:02 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "John"
<fireba8104@yahoo.com>
Well said. Cheers, John
Tesla list
<tesla@pupman.com> wrote: Original poster: "Gregory Hunter"
HUGE CHOP!!!!
> I too must think
> that the days of the
> spark gap coil are numbered. Not because there
> "are" good SSTCs out there,
> but because the will soon simply be the "best"
> TCs... Even "big" systems
> are coming to speed fast!! The record for a point
> to point arc is 59 feet...
I'm not picking on this particular comment. I've seen numerous similar comments
about the end of the spark gap Tesla coil from a number of posters over the past
few months. So the SSTC is going to do away with the old spark gap coils? You
mean the way auto racing did
away with horse racing? The way the cell phone did away with amateur radio? The
way the gun did away with archery? The latest SSTC work is really
amazing--nothing short of pioneering. But get a grip!
Nuff Said, Gregory R. Hunter. http://hot-streamer.com/greg
Date : Wed, 29 Sep 2004 08:14:04 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Mike"
<induction@comcast.net>
Hi Terry, Oh Yes, "DI" Water is very un-good. In fact, when we sell a water
cooled ceramic cap or "mushroom" cap, we put a sticker right on it that DI water
is NOT to be used or the warranty is void. DI water eats metal and thus the thin
barrier. Typically, a machine with these caps will start leaking at the barrier
in about 18 months as the metal has got so thin.
Steam distilled water is best and has no problems like DI water. The typical
tube generator does run just a bit over 50 percent out, so your 60 kW machine
will usually have a 120 KVA plate transformer. The solid state machines are
much better. In the 80 percent area and easier to cool on exchanger demand.
Because of the high currents and skin effect, most of that is I/R losses. And
yes, the water on the SCR's is indeed on the hot side but as long as the water
feed and drain manifolds are grounded to the frame on the way in and out of the
machine, any leakage stops there and does not go external to the heater itself.
I don't know who started the DI water is a good thing years ago but I do wish
they would go away. I run into this issue almost every day in tech support. DI
may have it's place but not when your metal is going to be eaten away in
critical places! Mike.
Date : Wed, 29 Sep 2004 08:14:38 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Greg Leyh"
>Original poster: "Steve Ward"
>Hey Terry,
>
>[snip]
>
> > I see that super high current IGBTs are really in demand now ;-)) But
> > monsters like the fabulous Powerex CM600HA-24H my be too heavily designed
> > for "power" when what we need is "current". It can "officially" do 1200
> > amps peak which is nice but I know we don't need the 4200 watts of power
> > dissipation ;-))
>
>Yeah exactly. They also didnt strive to minimize stray L inside the
>bricks either. Greg Leyh wrote an article on this... cant remember
>where to find it though. As we push these IGBTs harder and harder the
>little things like stray L inside the IGBT will add up quick! And
>heck, we'd be doing something bad if we dissipated over 50W per IGBT
>(unless it was a REALLY big system). Even with making 11 footers, my
>IGBTs stay cold to the touch.
Here's one paper addressing the inductances of internal busbar structures in
'brick' style IGBTs. We designed and built prototype brick IGBTs for both 3300V
and 6500V service. Test results are shown.
http://www-group.slac.stanford.edu/esd/IGBTPAC2003.pdf
Another paper addresses some of the issues regarding stacking IGBTs into a
500kV, 550A Marx Bank. http://www-group.slac.stanford.edu/esd/PESC04_Paper.pdf
The internal emitter inductance is important even for slow applications, since
this will
largely determine the survivability of the device during fault conditions such
as arcing
or overvoltage. Large or uneven emitter inductances can cause internal
ringing, hot
spots and voltage overshoots that can destroy the device.
Date : Wed, 29 Sep 2004 08:15:47 -0600. Subject : RE: DRSSTC thoughts...
Original poster: "McCauley, Daniel H"
>Dan - I see you used the model for streamer loading of 220K + 1pF/foot for a streamer load in your SPICE
>models. I was just wondering how well that worked for you? There is some concern that model is just "too
>simple" for some things, so I was curious if it worked well in this case?
It appeared to work well enough to the point where my PSPICE simulated
waveforms matched
those of my experimental waveforms (primary side) However, i wasn't
able to measure secondary
voltage directly, so i'm not sure how they matched on the secondary
side.
>I also note from Dan's book that he has "almost" as many "toys" as "I" do!! :o))
>However, Dan's data shows the primary current can almost double during a ground strike!! That is a critical
>bit of info!! Do the models show that behavior too?
Not sure. I never really got to simulating ground strikes. Maybe Steve
C. can comment
on the models he's been using.
Dan.
Date : Wed, 29 Sep 2004 08:16:20 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Harold Weiss"
Hi All,
Gregory's right. Us "Spark Forever!" members will still be coming up with
new designs for gaps, primaries and etc. My newest coils have primaries
embedded in UHMWPE. Just wish I had the time to tune it before the thon. David
E Weiss.
Date : Wed, 29 Sep 2004 12:17:15 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Dr. Resonance"
Dan: You can measure you sec output by using a 10 cm ground sphere and firing
your coil in a single shot mode. We use a string of diodes and 5 meg resistance
in series with our primary HV xmfr. It fires once every 8-10 seconds.
The peak potential is independent of the waveform and will be accurate within
3%. At least it will get you in the ballpark. Compare this to average of 70%
efficiency with the standard equation:
Vsec = Vpri *0.70 * SQR (Lsec/Lpri)
Dr. Resonance
>
> It appeared to work well enough to the point where my PSPICE simulated
waveforms >matched those of my experimental waveforms (primary side) However, i
wasn't able to >measure secondary voltage directly, so i'm not sure how they
matched on the secondary side.
Date : Wed, 29 Sep 2004 20:00:38 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Mike"
Hi Dr. Resonance, Well I did hook one up to a classic coil, used
the 3/8 water cooled tubing as the primary, one turn, also tried two, was
better ratio with one.
The heater was a Lepel 2.5 kilowatt and we ran it with an extra tank cap so
it was in the same area as the secondary with a larger ball as the end cap.
Made a nice discharge, clean, after we filtered the DC plate supply well.
With SCR on the plate transformer we were able to control the power out nice
also. Externalized the Grid /feedback coil so it took up frequency lock with
the secondary.
I was fun, we got a few feet out of it, was more interested in what the
target experiment we made it for was doing so that output was enough. Nice
thing about tubes, they don't get so upset at an unusual load.
When we were done, took it apart and moved to the next project.
You're right though, man, would I love to tie into a 300 or 600 kW machine.
Even the wire in the 2.5 driven secondary got warm, I would have used Litz
wire to wind it if we had plans to run it really long.
We often use Litz wire to cut down RF heating, works well. Place up north of
here makes Litz wire about as large as you wish, I think to at least the
equal of MCM-500 anyway.
Carries RF much better with less heating than standard wire. Regards, Mike.
Date : Wed, 29 Sep 2004 19:59:04 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Jim Lux"
> I don't know who started the DI water is a good thing years ago but I do wish they would go away.
The ARRL Amateur Radio Handbook, probably. Either there, or in some other
ARRL book, there's a whole discussion of watercooling (retrofit) a glass
envelope RF power tube, probably at 3kV anode voltage. The original person
probably used distilled water, and somewhere along the line, I'd guess that
the wording got changed to DI (hey, it's a better insulator.. it must be
better, right?)
While ARRL does have lots of practical data, the accuracy and vetting of
little technical details (like DI vs other water) is probably not what one
would expect. I had some back and forth with the editors about an article
published in QST for a 700V plate supply to replace a venerable tube based
supply and the picture showed a DMM connected with the tiny Radio Shack
style clipleads tangled with the power cord, etc. And, there were some
component rating and design safety issues. Not that it can't be done
safely, it's just that the pictures shouldn't encourage bad practices. The
author of the article responded directly to me, and made some assertions
which, while I hesitate to call them outright lies, would be tough to
validate (i.e. he claimed the wires in the photo were HV clipleads... which
made me wonder if he had ever seen real HV wire). I can fairly confidently
assert that the author had no HV design experience (where HV is defined as
>100V) based on his component selection and layout. What makes it worse is
that he's selling kits. I run into this issue almost every day in tech.
Date : Wed, 29 Sep 2004 20:01:39 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "Jimmy Hynes"
>If only the bigger IGBTs could withstand such abuse. I only run my CM300s at 2X their peak rating
Who say's they can't? I don't!
>50V is the "killer" there.... But above 30V does no addled good...
I can't find it now, but I had an application note that said the 50% failure
point was around 70-80v
>"Top of die" heat sinking is typically a "giant" disaster in the
>industry... Cray tried it but.... Disaster... Best to use old "thin die"
>bottom thermal dissipation teck there... Happily, within reach of "basement shops" these days ;-)))
Prolly still tough, but the idea was to put a piece of copper on it for sucking
up transients. it doesn't really have to move any net heat out, jut to make it
have more thermal capacitance
>About the cooling issues, especially the die's, and whole devices, I like water cooling
The problem was allowing the die to suck up more energy during the short bursts.
Getting the heat out of the heatsink is not a problem at all here.
Date : Thu, 30 Sep 2004 08:14:08 -0600. Subject : Re: DRSSTC thoughts...( DI Water)
Original poster: "GEORGE STEIN"
> > I don't know who started the DI water is a good thing years ago but I do wish they would go away.
>The ARRL Amateur Radio Handbook, probably.
Some number of years ago, the television transmitter at my station used 2
Varian Klystrons running in parallel to make 60 Kw output power. The collector
of these klystrons was surrounded by a large bucket thru which
large quantities of de-ionized water (DI) flowed for cooling. These collectors
were made of pure finned copper. I do not remember any problems with corrosion
or degradation of the collector after years of operation in direct contact with
DI water. George Stein.
Date : Thu, 30 Sep 2004 17:12:31 -0600. Subject : Re: DRSSTC thoughts...
Original poster: "robert heidlebaugh"
Jim: having worked with distilled water and ultra pure distilled water I do NOT
recommend its use for anything other than chemistry. It will corrode
anything but pure Nickel pipe. Even 304 and 316 stainless will dissolve in
it. Only water with lime added is non corrosive. Yes trace lime is added
to distilled water to stabilize it. I use liquid cooling with high
voltage, but I use mineral oil in my cooling electrodes and cool the oil with
water or
air. This works, but water direct is a poor choice with high voltage.
It simply will Not stay pure for very long, Even glass dissolves slowly.
Robert H.
Date : Mon, 04 Oct 2004 07:46:53 -0600. Subject : RE: DRSSTC thoughts...
Original poster: "Steve Conner"
>Maybe Steve
>C. can comment
>on the models he's been using.
Wow. It seems DRSSTC fever has finally hit Pupman :P
First of all, here is the PSpice simulation I use.
http://scopeboy.com/tesla/drsstc/drsstc.zip
Maybe Terry and Dan Mc would like to play with it. There are two simulations,
each has a preset list of displays and commands for Probe. If you run the .cmd
file in Probe, several plots should appear showing useful stuff.
It uses the parametric simulation feature to simulate the coil dozens of times
with different streamer loadings, and see the worst-case currents and voltages.
The expected spark length can also be predicted. There is another simulation
file that does the same but with different primary inductances, to help you find
the correct tuning point.
Qualitatively this sim seems to work quite well. It predicts the doubling of
primary current for extreme impedance mismatches (like heavy ground arcs) and so
on. And it also does a reasonable reproduction of the bizarre
waveform from my Tesla-2 run as a DRSSTC. But quantitatively it still has a way
to go!
To try and refine the model I am starting a series of streamer loading
experiments (these are a joint venture with the high voltage technologies group
at Strathclyde university)
http://scopeboy.com/tesla/experiment/
I'm using a similar method to what Terry did but over a wide range of breakrates
and bang energies (which can be accurately controlled on the OLTC II) I have
hardly any data yet, the little I do have suggests that a 36" streamer at
100bps, 66kHz has a shunt resistance of about 400k.
So far, I think that we can adequately model the streamer load as either a
series RC or a shunt RC circuit. This is a "rough approximation" that only holds
at a single frequency. But since the DRSSTC's output only contains a
narrow band of frequencies I don't see a problem.
I assume that the R and C vary in some way as a function of streamer length. At
the moment I believe that R is proportional to (1/Length) and C is proportional
to Length. But I wouldn't be surprised if there turned out to
be a squared or square root in there. The constant of proportionality will
probably depend on many things too, for instance the breakrate and the resonant
frequency. Steve C.
Date : Mon, 04 Oct 2004 13:10:04 -0600. Subject : RE: DRSSTC thoughts... A Mistook
Original poster: "Steve Conner"
The link I posted should have been....
http://scopeboy.com/tesla/drsstc/drsstc_sim.zip ,
Sorry all!
Steve C.
Date : Mon, 04 Oct 2004 13:12:22 -0600. Subject : RE: DRSSTC thoughts...
Original poster: "McCauley, Daniel H"
Yeah, it took long enough. I think Jimmy first mentioned his results more than
two years ago on this list and nobody took it serious!
Anyways, I'll take a look at the simulation.
>Wow. It seems DRSSTC fever has finally hit Pupman :P
>
>First of all, here is the PSpice simulation I use.
>http://scopeboy.com/tesla/drsstc/drsstc.zip
>
>Maybe Terry and Dan Mc would like to play with it. There are
>two simulations, each has a preset list of displays and
>commands for Probe. If you run the .cmd file in Probe, several
>plots should appear showing useful stuff.
Date : Mon, 04 Oct 2004 19:06:49 -0600. Subject : RE: DRSSTC thoughts...
Original poster: "Malcolm Watts"
On 4 Oct 2004, at 7:46, Tesla list wrote:
> Original poster: "Steve Conner"
>
> >Maybe Steve
> >C. can comment
> >on the models he's been using.
>
> Wow. It seems DRSSTC fever has finally hit Pupman :P
>
> First of all, here is the PSpice simulation I use.
>
http://scopeboy.com/tesla/drsstc/drsstc.zip
>
> Maybe Terry and Dan Mc would like to play with it. There are two
> simulations, each has a preset list of displays and commands for
> Probe. If you run the .cmd file in Probe, several plots should appear
> showing useful stuff.
>
> It uses the parametric simulation feature to simulate the coil dozens
> of times with different streamer loadings, and see the worst-case
> currents and voltages. The expected spark length can also be
> predicted. There is another simulation file that does the same but
> with different primary inductances, to help you find the correct
> tuning point.
>
> Qualitatively this sim seems to work quite well. It predicts the
> doubling of primary current for extreme impedance mismatches (like
> heavy ground arcs) and so on. And it also does a reasonable
> reproduction of the bizarre waveform from my Tesla-2 run as a DRSSTC.
> But quantitatively it still has a way to go!
>
> To try and refine the model I am starting a series of streamer loading
> experiments (these are a joint venture with the high voltage
> technologies group at Strathclyde university)
>
>
http://scopeboy.com/tesla/experiment/
>
> I'm using a similar method to what Terry did but over a wide range of
> breakrates and bang energies (which can be accurately controlled on
> the OLTC II) I have hardly any data yet, the little I do have suggests
> that a 36" streamer at 100bps, 66kHz has a shunt resistance of about
> 400k.
>
> So far, I think that we can adequately model the streamer load as
> either a series RC or a shunt RC circuit. This is a "rough
> approximation" that only holds at a single frequency. But since the
> DRSSTC's output only contains a narrow band of frequencies I don't see
> a problem.
>
> I assume that the R and C vary in some way as a function of streamer
> length. At the moment I believe that R is proportional to (1/Length)
> and C is proportional to Length. But I wouldn't be surprised if there
> turned out to be a squared or square root in there. The constant of
> proportionality will probably depend on many things too, for instance
> the breakrate and the resonant frequency.
Another factor which has been considered in the past would be the
width of the arc channel which would be dependent on current at the
point being considered and which would mostly influence R.
Malcolm
>
> Steve C.
Date : Mon, 04 Oct 2004 19:45:58 -0600. Subject : RE: DRSSTC thoughts...
Original poster: Terry Fritz
Hi Steve,
At 04:28 AM 10/4/2004, you wrote:
> >Maybe Steve
> >C. can comment
> >on the models he's been using.
>
>Wow. It seems DRSSTC fever has finally hit Pupman :P
It was a little too high tech for most of use to "get"... Steve's 130+
inch streamers, and now Dan's great book to explain it, allows the masses
to finally catch on ;-))
>First of all, here is the PSpice simulation I use.
http://scopeboy.com/tesla/drsstc/drsstc.zip
Should have been per your correction:
http://scopeboy.com/tesla/drsstc/drsstc_sim.zip
Gosh!! You read the MicroSim instructions didn't you ;-))) It works fine, but
I will have to spend more time figuring out what is going on... BTW - You can
"select" the silly title block and just delete it... It is just blocks and
default added text.
>Maybe Terry and Dan Mc would like to play with it. There are two
>simulations, each has a preset list of displays and commands for Probe. If
>you run the .cmd file in Probe, several plots should appear showing useful
stuff.
>
>It uses the parametric simulation feature to simulate the coil dozens of
>times with different streamer loadings, and see the worst-case currents and
>voltages. The expected spark length can also be predicted. There is another
>simulation file that does the same but with different primary inductances,
>to help you find the correct tuning point.
I was never able to get that parametric thing to work. It could have saved
me weeks!!! Now that there is a model with it working, I shall try and
figure it out!!
>Qualitatively this sim seems to work quite well. It predicts the doubling of
>primary current for extreme impedance mismatches (like heavy ground arcs) and
so on.
Dan's new book shows exactly that!!!
>And it also does a reasonable reproduction of the bizarre
>waveform from my Tesla-2 run as a DRSSTC. But quantitatively it still has a way
to go!
Just a matter of tweaking the values in.
>To try and refine the model I am starting a series of streamer loading
>experiments (these are a joint venture with the high voltage technologies group
at Strathclyde university)
>
>http://scopeboy.com/tesla/experiment/
Cool! It takes some real fancy equipment to refine the values and numbers and
all. Expensive stuff!! Best if it can be borrowed ;-))
>I'm using a similar method to what Terry did but over a wide range of
>breakrates and bang energies (which can be accurately controlled on the OLTC
>II) I have hardly any data yet, the little I do have suggests that a 36"
>streamer at 100bps, 66kHz has a shunt resistance of about 400k.
I think you asked about streamer impedances... It's been a long time, but check
here:
http://www.pupman.com/listarchives/1998/October/msg00290.html
http://hot-streamer.com/TeslaCoils/MyCoils/CWCoil/CWImpedance.txt
I wish others could add to this data... I hate to be the only one "making these
numbers up". I have been known to screw up :o)))
>So far, I think that we can adequately model the streamer load as either a
>series RC or a shunt RC circuit. This is a "rough approximation" that only
>holds at a single frequency. But since the DRSSTC's output only contains a
>narrow band of frequencies I don't see a problem.
They are an excellent tool for measurements!! They don't have spark gaps and
such burning up and all the complexities of goofy spark gap coils going on. The
OLTC is very "tame" too but the DRSSTC simulates coils that are
far more common.
>I assume that the R and C vary in some way as a function of streamer length.
>At the moment I believe that R is proportional to (1/Length) and C is
>proportional to Length. But I wouldn't be surprised if there turned out to
>be a squared or square root in there. The constant of proportionality will
>probably depend on many things too, for instance the breakrate and the
>resonant frequency.
Cool!! Earlier data (known as "old data") suggest R is very constant and C is
directly proportional to streamer length. But "new data" is very welcome ;-))).
Cheers, Terry.
>Steve C.
Date : Tue, 05 Oct 2004 07:39:19 -0600. Subject : RE: DRSSTC thoughts...
Original poster: "Steve Conner"
>I was never able to get that parametric thing to work.
Don't thank me, it was Richie B. who showed _me_ how to work it.
>I think you asked about streamer impedances... It's been a long time, but check here:
Ohhhhhh I get it!!!! It's (always 220k no matter what the length of the
streamer) in series with (1pF per foot)
I thought it was (220k in series with 1pF) per foot :P
I'm working with a shunt R-C equivalent circuit so my higher value of 400k
makes sense.
If I take your formula for my 36" streamer, I should get 220k + 3pF which
(unless I lost a decimal point somewhere) is equivalent at 66kHz to 3.15M ||
2.8pF. That's a lot more than 400k.
So either my streamers are less resistive than yours, or more capacitive. I
suspect the latter as I'm working in a small room with metal walls and
ceiling. (and it would be a shame to have to lose the "Always 220k"
hypothesis).
Steve C.
