How welding machine works

[q-cad]

Hello

this photo:
http://www.mig-welding.co.uk/forum/album.php?albumid=837&pictureid=4522

I have no knowledge about welding machines, i have seen only gas ones, but it doesn't mean i have no knowledge of electronics.
I need to repair M408 CitoArc.

There is module in this block diagram which is pysically PCB.
There is R1 which is wire feeding speed.
Q1: what kind of wire? for what?
M is described as wire feed motor, is it polarized so looks like thyristors are adjusting speed of motor.

Q2, What is Q2 there? It is described man/auto. Is it manual or automatic mode of wire feeding speed control?

Q3. there is S1 on schematic, any idea what it is?

Q4. What is F3 next to rectifier (diodes)? Is it temperature fuse?

Q5. What is CN2?

Q6. what is contractor? Is is just big relay which turn on or off 3 phase into bigger transformer?

Q7. This mysterious module has potentiometers: Vmax, Vmin, RTS and Ramp called slope on my other schematic.
I expect Vmin and Vmax ar related to min and max speed of wire transfer (whatewer it is).
So what could be slope and RTS?

Q8. I have read schematic from this module, to understand this would be nice to know how welding machine works. So sorry for stupid questions, i am just from different story (software).

 

[Wedg1e]

Q1: what kind of wire? for what?

MIG welders work by feeding steel wire (typically 1mm diameter or less) into the join between the pieces of metal being welded. As the weld current is transferred through this wire it becomes molten; more wire is constantly fed into the weld as it moves along the joint.

M is described as wire feed motor, is it polarized so looks like thyristors are adjusting speed of motor.

Correct. The more current that the weld requires (ie thicker parts), the faster the wire has to be fed into the molten weld pool.

Q2, What is Q2 there? It is described man/auto. Is it manual or automatic mode of wire feeding speed control?

The drawing isn't clear enough for me to read, so I can't make out which part you mean.

Q3. there is S1 on schematic, any idea what it is?

The drawing isn't clear enough for me to read, so I can't make out which part you mean.

Q4. What is F3 next to rectifier (diodes)? Is it temperature fuse?

I would say so, yes.

Q5. What is CN2?

The drawing isn't clear enough for me to read, so I can't make out which part you mean. I guess it's a connector...

Q6. what is contactor? Is is just big relay which turn on or off 3 phase into bigger transformer?

Yes.

Q7. This mysterious module has potentiometers: Vmax, Vmin, RTS and Ramp called slope on my other schematic.
I expect Vmin and Vmax ar related to min and max speed of wire transfer (whatewer it is).
So what could be slope and RTS?

Slope (or ramp) is how fast the current ramps up to the preset maximum (or how fast it ramps down to minimum).

I'll let someone else fill in the blanks

 

[q-cad]

Thx a lot, that kind of motor is that?