Kaizer DRSSTC I

Mads Barnkob, Thu Sept 17 2009, 08:24PM

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

Peak current: Ipeak = (Vin * t * D) / Lmag = (24 * (70000/1000000) * 0,5) / (575 * 10^-6) = 1460 mA

Irms = Ipeak * 0,577 = 842 mA

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.







Video!