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new drsstc based upon my new driver topology(Musical DRSSTC)

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LAN_403

Reaching

Tue Dec 11 2007, 10:49PM

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

its been a while since i build my drsstc 6, so i am ready for a new one.

after fiddling and tweaking a new higher voltage driver topology, i think im ready for a new drsstc based upon this new driver. its nothing really "new" but i think its worth a try.
i already powered up some fullbridges of brick igbts etc, with some good results.

this drsstc will be a "rock" solid and indestructible, but simple. i finished the driver and the fullbridge, calculated and simulated the primary and secondary coil, mmc etc. primary is finished too, so it wont take a long time to finish the whole thing.

the driver in basic is a simple secondary bottom feedback driver with a pair of ucc driver ics driving a fullbridge of complementary n and p channel mosfets. the advantage is that i can go with a higher voltage (+-70V) and relatively low current. with a 2,5:1:1 gdt for each halfbridge i get a voltage of around +-25V on each igbt gate with much higher currents. the rise and fall times are in the range of 40nS with a 8nF load on each gdt. thats pretty good i think. . a simple overcurrent detection with lm311 with a pulsewith adjustable monostable 555 is for current limiting.

the halfbridge has a build in voltage controller with a lm311 to regulate the charging current of the big 2200ÂµF 400V smoothing cap. after the cap has reached the 270V mark, the relais is triggered etc. a simple but verly useful circuit, allowing soft start and prevents for tripping breakers.

a temp fuse and a really ultrafast fuse etc are some other safety gigs. a high frequency filter will do the rest, so that nothing can harm the driver or the other equipment.

thats no high power "how can i make the biggest arcs" project. i really want a drsstc which is reliable,. switch on and it runs, and no more blown fuses or igbts. so everything is layed out to hold up twice or three times the voltage, twice or three times the current for twice or three times the time. every part that can heat up is heatsinked, every part that can get weird by rf is shielded etc.
performance is limited to around 1kW for the first tests. sure, the bridge can stand up twice or three times the power, but i think 1kW is more than enough for a "small sized" drsstc to create beatiful sparks..

Dr. H.

Wed Dec 12 2007, 03:45PM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Beautiful setup Reaching. It looks clean and tidy. I can't wait to see the finished coil. Keep up the good work.

. One question - what are the IGBTs for the bridge ?

Tom540

Wed Dec 12 2007, 08:23PM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617

It looks nice and promising and your CT's look like chocolate donut's.

I see you shielded the comparator etc but is there a ground plane on the bottom of that area as well to shield the bottom?

Dr. Dark Current

Wed Dec 12 2007, 08:30PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Looks good!

Just one thing, you said:
"the driver in basic is a simple secondary bottom feedback driver with a pair of ucc driver ics driving a fullbridge of complementary n and p channel mosfets. the advantage is that i can go with a higher voltage (+-70V) and relatively low current."

You aren't putting 70V on the gates right?

Electroholic

Wed Dec 12 2007, 08:56PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

i think hes running +/-70V on the primary side of the GDTs

Reaching

Wed Dec 12 2007, 09:53PM

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

jup. +-70volt primary voltage on the gdt. primary is 25 turn hf trifilar 0,5mm. secondary is 10turns 0.75mmÂ² 70:2,5 is around+-28V for the gates. and yes. the bottom is shielded too.

shield is grounded like it should be, and the igbts on the bridge are irg4pc50ud 600v 220A pulsed

Tonic

Wed Dec 12 2007, 10:09PM

Registered Member #528 Joined: Fri Feb 16 2007, 10:32PM
Location: Warsaw, Poland
Posts: 166

Beautiful!

Why you're using two GDT cores instead of one?

Reaching

Wed Dec 12 2007, 10:14PM

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

cause it was better to use 2 instead of one for the layout and the most important thing. two cores can deliver more power in the same amount of time than one core :P

Reaching

Sun Dec 16 2007, 02:04PM

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

Finished the secondary and primary coil today

secondary is 11cm in diamter and 46cm wound with 0,17mm wire.
Calculated resonant frequency: 137khz without toroid
measured resonant frequency 146,8khz without toroid.

yesterday i varnished the secondary and started spinning it . the result is really nice. a clean surface without bubbles and nipples, lol..

with my toroid i will get around 82khz resonant frequency.

the primary coil is 28cm outer diameter, 7 turns of 6mm copper tubing.. the coupling will be in the range of .16 to .19

Dr. Drone

Sun Dec 16 2007, 07:59PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

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