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Teslathon DRSSTC (6) First Light!!

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LAN_403

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Wed Jun 07 2006, 08:52PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

within the next few weeks i want to build a nice powerful drsstc for the first ctc-labs teslathon in germany. i want it to be special and powerful for demonstrations etc.

within 3 days i made the primary and the case out of 8mm acrylic glas.
the primary coil consists out of 7 turns 6mm copper tubing.
for the mmc i have 36 wima mkp10 0,22yf 1600volt lying around, and a fullbridge of 40n60Â´s already finished.

driver with overcurrent protection, overvoltage protection, etc, primary current feedback .(not finished, i need some time for the pcb)

i thought about a secondary with ca 11cm in diameter and 50cm in height, wound with 0,2mm or so for a fres of around 100khz

here are two pics

the drsstc has to be finished and working until 28.07.06 , thats a possible goal

Update 12.06.06

i finished breadboarding the driver and the overcurrent protection and made 2 nice pcbs which are nearly finished.
the mmc is finished and consists out of 25 wima mkp10 0,22yf 1600 volts for a total of 220nF 8kV dc, 3,2kv AC.

Update!__________________-

first Light on 18.06.06

i finished the whole coil and the electronics and did some testruns today, with realy good results.

heres the finished coil without toroid, i have to make a nice one

and heres a pic of the first testrun on resonant frequency or almost in tune, . the sat antenna is 1,1m away, not bad for the first testrun.

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Sat Jun 17 2006, 08:11AM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

some new infos. the last two days i was working excessively on my coil to get it to work and yesterday i made the first tests with a other secondary to try the primary current feedback out. first i had trouble with a way too high frequency but i solved the problem by reversing the wire direction on the 1:140 feedback CT. but this thing will not work properly on primary current, dont know why, so i made the first light tests with secondary bottom feedback which worked fine. the overcurrent protection does not work properly but i think with a bit of time i will get it to work.
the whole acrylic base is full of electronics
heres a pic of the electronics

updates will come soon, today i want to debug the overcurrent protection to make it work, then iÂ´ll try to get the primary current to work properly. the driver begins to oscillate at around 10volt but i get nearly no output when running on primary current feedback, maybe reversing the primary will help?

Steve Ward

Sat Jun 17 2006, 08:25AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

the driver begins to oscillate at around 10volt but i get nearly no output when running on primary current feedback, maybe reversing the primary will help?

Tuning is much more critical with primary feedback. Unlike secondary feedback, if its not pretty close to in tune, it wont do a whole lot but ring up the primary current really high.

Also, if its oscillating in the right frequency range (and not way too high) then the phasing is correct. reversing the primary connections does not alter the phasing with primary feedback. You are really sensing the current from the inverter, so you need to either swap the CT wires, or feed the CT primary through the other way, or invert your gate drive signal... If you dont see a distinct difference in oscillation behavior when you seemed to have switch the phasing, then you really didnt do anything (this got me once, when i tried swapping the TC primary connections with no change... i then realized why).

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Sat Jun 17 2006, 08:57AM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

mhh, okay, then it seems its all right, i get the right frequency, around 100 to 120khz with my primary circuit, 0,22yf 8kv cap and a 7 turn primary with an diamter of 24cm.
i changed back to primary current feedback and added a 1k resistor to the input of the 74hc00, now it seems to start oscillating at around 6 volt on the bridge. i made a scopeshot, looks like its fine but this is my first coil with primary current feedback so maybe someone tell me different.

heres the pic

measured without secondary in place, only primary circuit,. probes on primary, bridge voltage 6volt.
div 20v/cm 20yS/cm
current draw was 1A off time 0,35mS on time 140yS (i set the off time so high, otherwise i cant make a good scopeshot, its not the newest oscilloscope)
if i vary the on time by watching the scope the frequency locks perfectly in so i think it only switches on zero current, .

okay, measured the primary current with an calibrated 1/1000 CT
same settings as above ,6volt bridge voltage, div 50yS/cm 0,2v/cm

so what do you think, am i fine or not.

Steve Ward

Sat Jun 17 2006, 05:08PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Can you zoom in on the scope to show only 1-2 cycles of the CT output? Id like to see where the switching noise is. Zoom in on some of the last few cycles. It looks fine so far as i can tell (though your scope is pretty out of focus!).

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Sat Jun 17 2006, 06:04PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

hehe, yeah youre right, my scope is 22years old and has several bad contacts inside i think, expecially on the focus and trigger pots.though its hard to calibrate and to make pics from it, but from time to time it works ,
heres a pic of the last few cycles, 20v/div 20yS/div , bridge voltage 12 volt

i can show some pics of the current waveforms on the ct when my overcurrent protection pcb is finished, hope its all right,
and steve, its not your circuit so you cant compare it with your settings, the basics are the same, 74hc14,74hc109, but i use a 74hc00 for the set and reset of the 74hc109

Steve Ward

Sat Jun 17 2006, 07:36PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Ok, so what is that waveform you just posted? Was it from a CT? Or was it some voltage somewhere?

If its from the CT, them im mighty confused, because the switching noise seen would suggest that you are switching *before* the zero crossing, which would mean that somehow your driver can predict when the zero crossing would occur (though, its not very good at it).

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Sat Jun 17 2006, 08:56PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

the waveform is meaured at the primary with a bridge supply voltage of 12volts. i have to finish the overcurrent protection circuit, then i can make a few signal pics of the 1/1000 current CT and the 1/140 current transformer.give me a few hours

mhh, okay, it was the best i could do, my scope is to old to trigger properly so i had to trigger by hand, measured on the 1/1000 current transformer with 10R burden resistor in place. 0,1v/div 50yS/div

Hazmatt_(The Underdog)

Sat Jun 17 2006, 09:33PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Teach yourself how to flame polish the plexi and hearts will stop when they see it!

I do it with a small flame from my prop/oxy rig..but CR does it with a propane torch I think.

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Sun Jun 18 2006, 01:28PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

hehe, good idea, i have some small pieces of the plexi liying around so iÂ´ll try it.

new Update, finished the secondary,
looks nice and heavy

hrhr, first light today!!!!

i couldnt wait to test this monster and wired it together, the secondary is almost dry, lol,,. okay i set the on time to around 80ys , overcurrent protection for testing to 300A, looks good so far, around 70cm discharges in the wall, i have to build it upt in my testing room where i have more space for testing.. never thought that a primary feedback drsstc is so hard to adjust. i had to raise the secondary around 5cm to prevent racing arcs, maybe to high coupling or so.

heres a video of the first test, sorry its in german i cant speak english that good

so i think everything is fine, needs a bit more tuning and more space for testing and a nicer toroid,

*happy*

update__________________-

hrhr, forget the video, look at this pic,, the sat antenna is 1,1meter away , i played around with the coupling and the primary frequency until i got it, its not finetuned yet, maximum current setting is 350A , on time ca 100yS nothing more, thats a real monster

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