200A TIG AC/DC welding machine

[McMax]

Hi all,

this is my first post here and first of all I want to thank you for accept my registration.
My name is Max and I write from Milan, Italy.
Together with a friend we are working since almost 2 years to an open source project for a 200A AC/DC TIG welding machine.
For whom is not familiar with the arc welding this machine have to be capable to deliver 200A of current on the welding torch in DC or AC (square wave) with a frequency adjustable from DC to 250Hz.In the TIG mode there will be an arc starter which uses an HF HV (15KV) oscillator in order to generate a low power high voltage arc which will create the path for the high power low voltage welding arc without scratching the electrode as you normally do in a standard welding machine.
We have planned to built many functions which most of them will be software including unbalanced welding current on the two quadrants when in AC: the current of the positive quadrant can be different from the current of the negative quadrant.
All those functions are needed to solder many different types of metal and thicknesses.

Reading some of the posts in this forum I assume that you guys are more related to audio amplifiers so I don't want to bother you with this welding project so much if you're not interested.

The reason of my registration was mainly to share and ask opinions on this power supply which is not completed yet.

This morning we reached 200A output in DC mode with a 0.1ohm resistive load (immerse in water) and for the moment we've been able to solder in DC with a 70A arc (this is not TIG, standard MMA)
[video=youtube;qqXcv09q4D8]http://www.youtube.com/watch?v=qqXcv09q4D8[/video]


As I said we're still working on the project and there are many things that need to be adjusted so if you don't mind I'll ask for help when I need.
In the meantime, if there is another insane guy like me who is interested in some details for this project please don't hesitate to ask.
Most of the material is in Italian but I can translate and share pieces without any problem.

Max

 

[McMax]

And here some pictures just to show you how the monster looks like:

 

[Joea]

Hi McMax
That is really good work and i think you have well, i am not into making a welder but into induction forge to make knife blades and to harden without over heating.
Perhaps if you were to fit your welder outputs AC into a resonant circuit series parallel then it might work

Regards
Joe

 

[McMax]

Hi Joe,

thanks for the comments. You're right this could do an induction heating system as well.... but before thinking to additional features we need to finish the welding machine and test it
, test it and test it again until it burns for overheating

 

[m0gjr]

That doen't look like a 200 amp supply. I've been working on a simmilar project and that looks significantly lower rating than what i've found nessesary. What are the dimensions of the box? (Any other details would also be appreciated)

 

[Joea]

Hi McMax
Looking again at your photographs i would suggest that you avoid running individual cables through there own hole in the same sheet of metal as this will set up eddy currents in the sheet metal, and as you are dealing with high powers there might be some danger in melting the aluminium sheet

Regards
Joe

 

[McMax]

@m0gjr what exactly do you think is lower rated? 50 sq.mm of copper for the cables are not enough? power pcb milled from a 1.6mm thick pure copper sheet are not enough? the heat sink is 120x120x300mm aluminium....

@joea do you think there's really a risk to melt te aluminium? the transformer is closed in the box to help the heat dissipation with the fan....

 

[Joea]

Hi McMax

You have slightly misunderstood, it is not the location of the Ttansformer or the size of the windings, it is the fact that the wires are going through the aluminium in individual holes, this will set up an eddy current in the aluminium between the two holes, this will then heat the aluminium, the longer you use the welder the hotter it will get, also as current is being used to heat the aluminium it is then no longer available to be used in welding.

I hope this is clearer

Joe

 

[m0gjr]

no the cables are fine it just looks rather small, what do you actually have in it (circuit would help)

 

[McMax]

m0gjr you're right I realize just now I've posted the pictures of the first version when the primary switch board was built with only 1 IGBT per side. The new version uses 3 MosFETs (FCA22N60 fairchild) per side, 12 MosFETs total, driven by Silicon Labs SI8234 Isolated gate drivers.
Here some pictures of the primary switch board and all the assembly including the gate driver board which is mounted on the top. The primary switch board is made on two layer PCB milled from an assembly of two 1.6mm copper sheet.
Here a couple of waveforms of the gate drive signals (high side) and the transformer primary. We're now working to improve the symmetry of the switching since, as you can see, are not perfectly the same on both sides of the bridge. Time base is 5uSec/cm and Vbus is 310Vdc.
The schematic is relative to the gate driver board; the power switch board has just the 12 MosFETs and a 22uF (now 68uF) electrolytic cap. The total capacitance of the VBUS line is 4000+68uF rated at 450VDC.

 

[m0gjr]

I was more after the whole circuit schmatic, i find it difficult to belive that you've got a mains input pfc (you cant draw that sort of power without it) main switcher for the transformer and an output switcher for the ac welding all in that little box

 

[McMax]

Box ? Which box ?? You have not seen any box in my pictures since I've just put the picture of the HEATSINK !
About the PFC: NO PFC AT ALL, for the moment !

 

[m0gjr]

You know what i mean, two heatsinks bolted together.

So you can draw 5 kw from your mains with no pfc?!

 

[m0gjr]

And are there no components inclosed by the heatsink? i still cant see the transformer and rectifier.

 

[stewin]

wow great work congrats. can it solder aluminum or other metals or it is just steel? also pls post full schema.

 

[AutoclassA]

Are there any diagrams to be released?

 

[ultra]

50 sq.mm of copper for the cables are not enough? power pcb milled from a 1.6mm thick pure copper sheet are not enough? .

My compliments ! I see some very clever mechanical solutions, and ...a lot of copper so far.

Keep up the good work.