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Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
It have been a long time since I first saw a DRSSTC in action and immediately fell in love, but knowing damn well I at that point was in no state to build one, or simply just understand it works.
Many moons have passed, many threads and fewer books have been read, hopefully it will have paid off to wait with building one till I felt it was time :)
Greatest inspiration for this coil must be Steve Wards DRSSTC-1
updated: 6th November 2010
Specifications Resonant frequency Around 70 KHz
Secondary 160 mm diameter x 605 mm height , 2200 turns of 0.25 mm enamelled wire
Topload 630 diameter x 130 mm ducting diameter, dryer ducting, this is subject to change
Primary 320 mm diameter x 150 mm height, 9 turns of 10 mm copper piping ~ 28,27 mm^2, tapped at 5.5
Bridge Fullbridge of IXGN60N60C2D1 IGBTs, SOT-227 package 150 mm length x 80 mm width x 90 mm height, 1 KG of heatsink 2 x 3300uF 450V BHC capacitors for 6600uF bridge filtering. (each: ESR 39mOhm@100Hz, Z 27mOhm@10kHz and 53A Iripple@70KHz@50 Degrees celcius)
MMC 6 Strings of 2, 942C20P15K-F 0.45 uF rated 4000 V and 81 A Irms
Timeline
20th March 2009 Bought 30x IXGN60N60C2D1 from digikey usa, import taxes etc almost killed me
7th April 2009 Bought 60x 942C20P15K-F capacitors through dr.spark, again hello import taxes
15th May 2009 Bought heatsinks cheap from germany
19th May 2009 Started converting Wards latest drsstc driver to single sided board
23rd July 2009 Started 3D designing the fullbridge
It is bulky, on 2 heatsinks with capacitors between them, its too big and needs to be overhauled.
23rd August 2009 Redesigned the fullbridge
The two IGBTs in the middle are turned 180 degrees to have the supply at one side of the heatsink and output on the other, it got compact, neat and only one overlap with busbar, I am very happy with this design.
24th August 2009 Made a spreadsheet to ease experimenting with different DRSSTC settings, this was also a try to collect some of the different theory and put it side by side, it might not all make sense
27th August 2009 Bought 50 meter of 10 mm copper tubing, two drain pipes 160 mm diameter x 1000 mm and 1,5 mm copper sheet.
Also in the picture there is worth noticing the current transformers harvested from industrial Siemens overcurrent protectors, they are for 690VAC 200A, but might be useful at higher frequencies, this will show later on, they do look like 1000 turn.
8th September 2009 Finished converting Wards latest drsstc driver to single sided board
12nd September 2009 Finished assembling the single side board ward drsstc driver
16th September 2009 Etched, assembled, tested and housed interrupter with burst mode
19th September 2009 Cut out busbar from copper sheet and assembled IGBTs, heatsink, capacitors with busbar, home made 8mm brass spacers are used. Leads to the primary are 16mm^2 stranded 90 Degree celcius machine tool wire.
25th September 2009 Found a aluminum box and transformer for the driver, wound a GDT and started preparing decoupling capacitors, TVS and zeners for the bridge.
With all the wonderful theory about GDTs in the wiki, it would be a shame not to check it out instead of just going for a high permeability core with 10 turns on CAT5 cable. So here goes
Its a Epcos ringcore, material: N30, good up to 5MHz, Aemm^2: 95,89, AL: 5750nH
Inductance with 10 turns: L = AL * N^2 = 5750 * 10^2 = 575 uH
Minimum number of turns needed to avoid saturation
t, 50% duty cycle = (1 / 70000) / 2 = 7,3*10^-6
Nmin = ( V x t ) / ( B x Ae ) = (12 * (7,3*10^-6)) / (0,2 * (95,89*10^-6)) = 4,6 turns
Current needed to drive a single 60N60 IGBT gate
I = ( C * V ) / t = ((3,9*10^-6) * 24) / (7,3*10^-6) = 12,8 mA, including magnetising current, double this figure.
So it all seems to have overhead enough to drive a full bridge.
3rd October 2009 Started on contruction of the MMC
10th October 2009 Made the round platform plates for the coil to be built on, they were cut out from 19 mm MDF wood plates with a modified router, also shown in the picture, very neat for making circular cuts.
11th October 2009 Finished MMC construction, features a 80 mm fan that delivers 30 cubicmeters/hour of air.
5th November 2009 Debugged PCB design of the driver
Tested driver and interrupter on a small DRSSTC I put together just for testing purpose, blew the half bridge when I ran it in CW without feedback, I guess there is no way I could have treated that poor little coil any worse...
12th December 2009 Made primary form and winded the primary coil onto it, with a strike rail and mounted on the upper platform, took me 1½ hours just to wind the coil through the holes and also spend quite some WD40 :D
The coil is a true helical coil with 4 mm steps between the supports
27th March 2010 It sucks to wind around half a secondary to learn that you used a ruler with 2 scales and you starter with 100 mm offset in the wrong direction...
The second try on the secondary was winded in 2 hours using my new coil winder rig, its 2200 turns of 0,25 mm enamelled wire on a 160 mm diameter pipe, winding length is 605 mm, its currently hardening its second layer of varnish till I get time to visit my parents again as its staying at their garage while getting varnished.
2nd August 2010 I made a fitting piece for holding the CTs as the cable shoes were too wide to go through the CTs
7th August 2010 Today I assempled some of the parts on the platform, its beginning to look like a DRSSTC! Also I painted it black some weeks ago!
Its all wheels under the bridge...
9th September 2010 The topload is done, measuring 130 x 620 mm, made from aluminium ducting on a wooden form, smoothed with filler for metal and covered in aluminium tape.
17th October 2010 Final testing of driver features, got a 555 acting as a feedback at 70KHz while my signal generator is used to simulate over current input signal.
Test setup of the nopw ready to run coil! Still need some minor details before its finished :)
FIRST LIGHT! YIPEE!
5th November 2010
150 centimeter long sparks! Running from 250VAC in at 10A, 9 cycles ~200-225uS on-time, 500A limiter.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
brtaman wrote ...
Looking good Mads!
Looks like you have a lot of work ahead of you, can't wait to see your finished product! Your going to use the DRSSTC1 driver, correct?
The board you can see in the picture with materials is actually wards latest driver, further pictures, layout files etc will be posted once its debugged etc :)
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
brtaman wrote ...
Great bridge design, inductance kept at a minimum! How do you keep your copper looking so clean? Did you apply anything to it?
I wondered the same thing...How do you do it? I know some people told me you could apply even a thin coating of varnish to it, clear varnish, to protect it...but this doesn't appear to be the case.
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Kaizer DRSSTC I
