Long pulse DRSSTC pictures
Steve Ward, Sun May 21 2006, 06:53PMI always liked the look of the old SSTC sparks, how they are so thick and gnarled. So to achieve that effect with a DRSSTC, ive run it in single shot mode, and 5-8mS pulses. The primary current peaks to 900A+ after about .75mS, then decays to around 150A for the last 3-5mS where it stays relatively constant. With careful tuning, i managed to make the primary current *decrease* with ground strikes. Without careful tuning, the primary current will *increase* with ground strikes, and hold over 1000A for many mS!! The DC filter caps are charged to about 220VDC, and are left with about 60VDC when a single shot is over... that means 245J is used up in a single bang!! The target is set to 36", but a few of the sparks reached out to 40" and one even hit a controller on my shelf at 48". Im already thinking about how to get even bigger sparks
. I find it particularly interesting that so many branches are formed on a single shot (all pictures are single shots).Pictures are posted here:
http://www.stevehv.4hv.org/DRlongpulse/
Enjoy!
Re: Long pulse DRSSTC pictures
Marko, Sun May 21 2006, 07:10PM
Wow, I also like The Hot arcs
I must admit it doesn' look mighty like 100% CW bit it's still absolutely awesome.
Great work!
Marko, Sun May 21 2006, 07:10PM
Wow, I also like The Hot arcs
I must admit it doesn' look mighty like 100% CW bit it's still absolutely awesome.
Great work!
Re: Long pulse DRSSTC pictures
Steve Ward, Sun May 21 2006, 07:17PM
I still want a 10kW CW system
.
I guess i will just keep going till something blows up, then back off a little (normal proceedure). Though, i think a coil like this could really benefit from a higher Z tank circuit. Im considering building a whole new DRSSTC specifically for this type of operation.
Steve Ward, Sun May 21 2006, 07:17PM
I still want a 10kW CW system
.I guess i will just keep going till something blows up, then back off a little (normal proceedure). Though, i think a coil like this could really benefit from a higher Z tank circuit. Im considering building a whole new DRSSTC specifically for this type of operation.
Re: Long pulse DRSSTC pictures
..., Sun May 21 2006, 07:31PM
Wow, very impresisve!
Kind of hard to imagine that the energy used for that streamer is the same as a a 1g projectile going at like mach 2
..., Sun May 21 2006, 07:31PM
Wow, very impresisve!
Kind of hard to imagine that the energy used for that streamer is the same as a a 1g projectile going at like mach 2
Re: Long pulse DRSSTC pictures
HV Enthusiast, Sun May 21 2006, 08:34PM
Nice work Steve - cool photos. Looks like you just accidentally stumbled on one of the biggest challenges with solid state radar systems these days, the elusive long pulse. Anyways, the challenge of course is to maintain voltage across the entire pulse to deliver constant energy through the entire pulse.
I propose the next part of your experimentation would be to achieve the long pulse, but with maintaining constant voltage across the entire pulse with constant meaning a few voltage drop maximum at the bridge rails. I'd be curious to see how that compares with what you are doing now.
To do this, you could simply make a discrete linear regulator (read that as new COOL project!) and use a fairly large capacitor bank (size you can determine with simulation) to drive it. Say charge the capacitor bank to maybe 400V or whatever it takes to maintain headroom on the regulator across the entire pulse, and regulate at 220V at the input to your bridge. With enough bandwidth, this should work quite well. Sure, it will be pretty inefficient, but for a single non-repetivie pulse, should be fine for experimentation.
BTW, i really hope you weren't doing this on your 21st Birthday weekend . . . You should be out drinking your brains out and letting loose . . . Or at least spending all day sunday in bed with a massive hangover !
Dan
HV Enthusiast, Sun May 21 2006, 08:34PM
wrote ...
The DC filter caps are charged to about 220VDC, and are left with about 60VDC when a single shot is over... that means 245J is used up in a single bang!! The target is set to 36", but a few of the sparks reached out to 40" and one even hit a controller on my shelf at 48". Im already thinking about how to get even bigger sparks
The DC filter caps are charged to about 220VDC, and are left with about 60VDC when a single shot is over... that means 245J is used up in a single bang!! The target is set to 36", but a few of the sparks reached out to 40" and one even hit a controller on my shelf at 48". Im already thinking about how to get even bigger sparks
Nice work Steve - cool photos. Looks like you just accidentally stumbled on one of the biggest challenges with solid state radar systems these days, the elusive long pulse. Anyways, the challenge of course is to maintain voltage across the entire pulse to deliver constant energy through the entire pulse.
I propose the next part of your experimentation would be to achieve the long pulse, but with maintaining constant voltage across the entire pulse with constant meaning a few voltage drop maximum at the bridge rails. I'd be curious to see how that compares with what you are doing now.
To do this, you could simply make a discrete linear regulator (read that as new COOL project!) and use a fairly large capacitor bank (size you can determine with simulation) to drive it. Say charge the capacitor bank to maybe 400V or whatever it takes to maintain headroom on the regulator across the entire pulse, and regulate at 220V at the input to your bridge. With enough bandwidth, this should work quite well. Sure, it will be pretty inefficient, but for a single non-repetivie pulse, should be fine for experimentation.
BTW, i really hope you weren't doing this on your 21st Birthday weekend . . . You should be out drinking your brains out and letting loose . . .
Or at least spending all day sunday in bed with a massive hangover ! Dan
Re: Long pulse DRSSTC pictures
Terry Fritz, Sun May 21 2006, 11:58PM
VERY cool! Steve!!
I see the corkscrew effect shows up very well here. Almost unimaginable single shot power!!!
Much to ponder....
I did that... Your better off staying home You can always turn into a rock star like Steve C. latter
I spent all weekend working on MOT charging systems...
Cheers,
Terry
Terry Fritz, Sun May 21 2006, 11:58PM
VERY cool! Steve!!
I see the corkscrew effect shows up very well here. Almost unimaginable single shot power!!!
Much to ponder....
BTW, i really hope you weren't doing this on your 21st Birthday weekend . . . You should be out drinking your brains out and letting loose . . . Or at least spending all day sunday in bed with a massive hangover !
I did that... Your better off staying home
You can always turn into a rock star like Steve C. latter I spent all weekend working on MOT charging systems...
Cheers,
Terry
Re: Long pulse DRSSTC pictures
HV Enthusiast, Mon May 22 2006, 01:01AM
I wonder if both of the following would exhibit the same cork screw behaviour.
1. Approaching CW (low PRF, long pulsewidth)
2. Approaching CW (very high PRF, short pulsewidth)
In either case, the system is approaching CW mode of operation, but short vs. long pulsewidth. Could be another interesting experiment.
HV Enthusiast, Mon May 22 2006, 01:01AM
I wonder if both of the following would exhibit the same cork screw behaviour.
1. Approaching CW (low PRF, long pulsewidth)
2. Approaching CW (very high PRF, short pulsewidth)
In either case, the system is approaching CW mode of operation, but short vs. long pulsewidth. Could be another interesting experiment.
Re: Long pulse DRSSTC pictures
Part Scavenger, Mon May 22 2006, 02:47AM
Geez, don't encourage him to waste brain cells. If he's got extra, please send them to me! Your's are top quality Steve!
That's pretty cool stuff with the hot arcs! Love the pics.
Part Scavenger, Mon May 22 2006, 02:47AM
Geez, don't encourage him to waste brain cells. If he's got extra, please send them to me! Your's are top quality Steve!
That's pretty cool stuff with the hot arcs! Love the pics.
Re: Long pulse DRSSTC pictures
Tesladownunder, Mon May 22 2006, 04:34PM
Impressive at 245j/bang. This is what 2500J/bang is like
(with the little help of a very thin wire to start things off..)
Peter
Tesladownunder, Mon May 22 2006, 04:34PM
Impressive at 245j/bang. This is what 2500J/bang is like
(with the little help of a very thin wire to start things off..)
Peter
Re: Long pulse DRSSTC pictures
coaster_chris, Mon May 22 2006, 05:48PM
@TDU
*SIGH* You and your big caps....
Steve, that are for shure some realy impressive streamers! What a length for a DRSSTC! Well done m8!
Chris
coaster_chris, Mon May 22 2006, 05:48PM
@TDU
*SIGH* You and your big caps....
Steve, that are for shure some realy impressive streamers! What a length for a DRSSTC! Well done m8!
Chris
Re: Long pulse DRSSTC pictures
EEYORE, Mon May 22 2006, 06:06PM
I used to run my first drsstc this way...I would set the modulator for 10ms and have about 1bps. My power supply was a voltage doubler using two 10,000uF 400volt electrolytics. The sparks looked just like those and were very intimidating, just not nearly so long...Despite much anxiety, I never did lose any parts this way...
Matt
EEYORE, Mon May 22 2006, 06:06PM
I used to run my first drsstc this way...I would set the modulator for 10ms and have about 1bps. My power supply was a voltage doubler using two 10,000uF 400volt electrolytics. The sparks looked just like those and were very intimidating, just not nearly so long...Despite much anxiety, I never did lose any parts this way...
Matt
Re: Long pulse DRSSTC pictures
Steve Conner, Mon May 22 2006, 07:25PM
Whee, good stuff Steve! O_O 245J is very impressive. I bet it's about the same bang energy as Bill Wysock's Super Model 13 or something. As for maintaining the DC bus voltage throughout the burst, who cares, it's not rocket science
Steve Conner, Mon May 22 2006, 07:25PM
Whee, good stuff Steve! O_O 245J is very impressive. I bet it's about the same bang energy as Bill Wysock's Super Model 13 or something. As for maintaining the DC bus voltage throughout the burst, who cares, it's not rocket science
Re: Long pulse DRSSTC pictures
Steve Ward, Tue May 23 2006, 12:37AM
Well, im up to 4 foot solid sparks now, and the base of the spark looks to be about 1" thick . I found a neat trick to produce these sparks. First, send out 3-5 good "bangs" quickly to form a long, thin streamer channel. Then, on the final bang, let it ring out for 3-5mS so as to build up all that plasma that surrounds the spark. It just so happens that this is the exact sequence of events that happens with my over-current limiter scheme.
But, soon (probably tomorrow) im going to test out a "PWM" scheme instead, where when the current reaches its limit, only 1 or 2 RF cycles are cut out, and then the inverter resumes adding energy. Im still not sure what the transient and steady state response will be on the primary, im hoping it will decay like one long burst does, but keep the primary current to a more sane level (ive been running 1000A regularly now). More on that when i actually test it.
Steve Ward, Tue May 23 2006, 12:37AM
Well, im up to 4 foot solid sparks now, and the base of the spark looks to be about 1" thick
. I found a neat trick to produce these sparks. First, send out 3-5 good "bangs" quickly to form a long, thin streamer channel. Then, on the final bang, let it ring out for 3-5mS so as to build up all that plasma that surrounds the spark. It just so happens that this is the exact sequence of events that happens with my over-current limiter scheme. But, soon (probably tomorrow) im going to test out a "PWM" scheme instead, where when the current reaches its limit, only 1 or 2 RF cycles are cut out, and then the inverter resumes adding energy. Im still not sure what the transient and steady state response will be on the primary, im hoping it will decay like one long burst does, but keep the primary current to a more sane level (ive been running 1000A regularly now). More on that when i actually test it.
Re: Long pulse DRSSTC pictures
Steve Conner, Tue May 23 2006, 01:14PM
Wow, that's crazy! I've got to try this. I already have the PWM current limiting on my coil, so it should just be a case of changing one little cap in the interrupter, for one 10 times bigger.
Having said that, I found that when I do the longest burst I can on my coil (300us at the moment) the streamer seems to split and fork a lot. It looks for all the world like a tree that shed its leaves in winter. But maybe making it longer still, one of the branches will dominate and the others die out?
Steve Conner, Tue May 23 2006, 01:14PM
Wow, that's crazy! I've got to try this. I already have the PWM current limiting on my coil, so it should just be a case of changing one little cap in the interrupter, for one 10 times bigger.
Having said that, I found that when I do the longest burst I can on my coil (300us at the moment) the streamer seems to split and fork a lot. It looks for all the world like a tree that shed its leaves in winter. But maybe making it longer still, one of the branches will dominate and the others die out?
Re: Long pulse DRSSTC pictures
Desmogod, Wed May 24 2006, 12:56AM
Maybe the heating of the air by previous discharges gives the streamer a "warm" path to arc through and prevents the branching?
Desmogod, Wed May 24 2006, 12:56AM
Maybe the heating of the air by previous discharges gives the streamer a "warm" path to arc through and prevents the branching?
Re: Long pulse DRSSTC pictures
Steve Conner, Sun Jul 02 2006, 09:20PM
OK, I modified my interrupter with a switch that makes the pulse 10 times longer, so it can go up to 3ms now. The results are pretty cool!
A 3ms burst drains the filter cap drastically, and makes a dull POP! noise like a flashgun going off but much louder. When I fire one with the cap charged to 300V, it grows a streamer that looks like a 3ft white tree. It looks much the same as what I get when the coil is doing 250us bursts repetitively at 100-200Hz, but thicker and blue-white. The breakout point flashes bright white as if it was actually glowing white hot for the duration of the pulse.
The current limit indicator doesn't light, so I guess the primary current is staying below the 400A setpoint of its own accord.
I'm doing a demonstration at the uni High Voltage Technologies Group on Thursday, and I'll try and get some pics of these crazy looking sparks while I'm there, and do some ground strikes too. I don't much like doing ground strikes in my house.
Steve Conner, Sun Jul 02 2006, 09:20PM
OK, I modified my interrupter with a switch that makes the pulse 10 times longer, so it can go up to 3ms now. The results are pretty cool!
A 3ms burst drains the filter cap drastically, and makes a dull POP! noise like a flashgun going off but much louder. When I fire one with the cap charged to 300V, it grows a streamer that looks like a 3ft white tree. It looks much the same as what I get when the coil is doing 250us bursts repetitively at 100-200Hz, but thicker and blue-white. The breakout point flashes bright white as if it was actually glowing white hot for the duration of the pulse.
The current limit indicator doesn't light, so I guess the primary current is staying below the 400A setpoint of its own accord.
I'm doing a demonstration at the uni High Voltage Technologies Group on Thursday, and I'll try and get some pics of these crazy looking sparks while I'm there, and do some ground strikes too. I don't much like doing ground strikes in my house.
Re: Long pulse DRSSTC pictures
Marko, Sun Jul 02 2006, 10:19PM
I ran my DRSSTC at about 500us continuously, producing about a 40cm long, very neat looking CW-ish spark until it died. I seem to have some energy loss problems because of coupling to ferrous metal plate under the primary, thin primary wire, MKT caps, and only halfbridge drive also add up :/
Look of spark is a bit washed out because of long-ish exposure..
Marko, Sun Jul 02 2006, 10:19PM
I ran my DRSSTC at about 500us continuously, producing about a 40cm long, very neat looking CW-ish spark until it died. I seem to have some energy loss problems because of coupling to ferrous metal plate under the primary, thin primary wire, MKT caps, and only halfbridge drive also add up :/
Look of spark is a bit washed out because of long-ish exposure..
Re: Long pulse DRSSTC pictures
Steve Conner, Thu Jul 06 2006, 02:33PM
OK here we are...... These pictures are of 3ms single shot bursts which have an energy of about 50J. They look pretty neat!
While firing these off, I had a number of primary-to-secondary flashovers. I think one of these developed into an arc between primary turns, because there was a pretty loud bang and I saw pieces of molten copper fly. Afterwards I could see a tiny crater blown out of the copper pipe. However the electronics all still work fine
This was done in one of the Faraday cages at Strathclyde University's High Voltage Technologies Group, as part of their open day tour.
Steve Conner, Thu Jul 06 2006, 02:33PM
OK here we are...... These pictures are of 3ms single shot bursts which have an energy of about 50J. They look pretty neat!
While firing these off, I had a number of primary-to-secondary flashovers. I think one of these developed into an arc between primary turns, because there was a pretty loud bang and I saw pieces of molten copper fly. Afterwards I could see a tiny crater blown out of the copper pipe. However the electronics all still work fine
This was done in one of the Faraday cages at Strathclyde University's High Voltage Technologies Group, as part of their open day tour.
Re: Long pulse DRSSTC pictures
Steve Ward, Thu Jul 06 2006, 04:25PM
Awesome pics Steve . Was your current limiter kicking in much?
Im almost tempted to try this on my big coil... Could you imagine 8+ footers looking like that?
Steve Ward, Thu Jul 06 2006, 04:25PM
Awesome pics Steve
. Was your current limiter kicking in much? Im almost tempted to try this on my big coil... Could you imagine 8+ footers looking like that?
Re: Long pulse DRSSTC pictures
HV Enthusiast, Thu Jul 06 2006, 06:09PM
Lookin' good Steve. Now its time to beef up the pulse. With my new modulator, and a huge honkin' capacitor bank behind it, i'm running about 20ms pulses which are pretty spectacular. Of course, you need a lot of capacitance behind it to minimize the droop to maintain energy transfer.
I've also experimented with hooking up a rectified high voltage source, gated with the pulse (normal continous operation) and fed into the base of the secondary. This provides some nasty serious ground arcs - extremely loud. And QUITE dangerous!
HV Enthusiast, Thu Jul 06 2006, 06:09PM
Lookin' good Steve. Now its time to beef up the pulse. With my new modulator, and a huge honkin' capacitor bank behind it, i'm running about 20ms pulses which are pretty spectacular. Of course, you need a lot of capacitance behind it to minimize the droop to maintain energy transfer.
I've also experimented with hooking up a rectified high voltage source, gated with the pulse (normal continous operation) and fed into the base of the secondary. This provides some nasty serious ground arcs - extremely loud. And QUITE dangerous!
Re: Long pulse DRSSTC pictures
Steve Conner, Thu Jul 06 2006, 06:45PM
EVR: Can we see some pics of your 20ms pulses?
Steve: The current limiter was set to 400A and it didn't seem to be kicking in. With the tuning I use, streamer loading and ground strikes seem to decrease the primary current. I'd love to see this done on your big coil, but be sure to wear shrapnel proof pants. >_<
Steve Conner, Thu Jul 06 2006, 06:45PM
EVR: Can we see some pics of your 20ms pulses?
Steve: The current limiter was set to 400A and it didn't seem to be kicking in. With the tuning I use, streamer loading and ground strikes seem to decrease the primary current. I'd love to see this done on your big coil, but be sure to wear shrapnel proof pants. >_<
Re: Long pulse DRSSTC pictures
Marko, Thu Jul 06 2006, 07:02PM
I had an idea from longer ago to put a big high energy cap 'under' the secondary so it passes RF and seccondary acts as pilot transformer, creating huge loud discharge once it contacts ground.
I guess that would turn a coil in real killer machine over there.
Marko, Thu Jul 06 2006, 07:02PM
I had an idea from longer ago to put a big high energy cap 'under' the secondary so it passes RF and seccondary acts as pilot transformer, creating huge loud discharge once it contacts ground.
I guess that would turn a coil in real killer machine over there.
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