Question about AC welding machine

M

Mutt

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So I see a alot of videos of people making good spot welders outta microwave transformers. I took a microwave apart today (Panasonic) and it had the most ridiculously cheap transformer I have ever seen. Not even sure how it even worked. It was mostly plastic and the fewest winding of I have ever seen. So my question is this

Since that AC transformer just loses it secondary windings and some 2/0 welding cable is just double wrapped it in it's place and the rest of the machine just hobbled together from scrap laying around, I got to thinking. Why wouldnt it be possible to just install a couple of tapered copper mig welding tips into the electrode and ground holders of a AC welding machine and just use the welding machine for the current? I mean, you could make some tongs outta steel and screw the tips into it for better control, but will this work, or will the welder short circuit or something? Or better yet, turn the tig welder on AC and be able to use the pulse (timer) function and the foot pedal or hand trigger for better control
 
I think the closed circuit voltage is too high and may result in some spatter
The mot transformer spot welder i made was copied from the web, it used few turns of heavy cable to top out at about 3-4v open circuit
It works for razor blades and thin materials

The real deal units are DC powered
 
the videos I watched most all weld 2 5/32 diameter nails together, another will melt a 16 penny nail in under 10 seconds.
 
The Panasonic transformer you saw was probably a ferrite core high frequency transformer which are common in the new inverter designs. Totally different animal than the older iron core transformer which experimenters like to modify.
Mike is correct in that a conventional arc welder won't make a good spot welder. You need high current but at a much lower voltage than used for arc welding- around 3 volts compared to 30 volts
-Mark
I think it requires at least two of the iron core microwave oven units to get enough amperage, and it's getting harder to find those larger scrap ovens
If you have an old arc welder you can sacrifice, that would work- change the secondary winding
 
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A cheap old transformer arc welder has the perfect transformer. I've made a spot welder this way, ended up about 3V, 1300A. I rewound it with thicker primary and a 2 turn secondary with 80mm^2 cable. Trouble is I was too successful and it draws 40A on the primary, which is way too much for a plug in appliance.
 
markba633csi said:
The Panasonic transformer you saw was probably a ferrite core high frequency transformer which are common in the new inverter designs. Totally different animal than the older iron core transformer which experimenters like to modify.
Mike is correct in that a conventional arc welder won't make a good spot welder. You need high current but at a much lower voltage than used for arc welding- around 3 volts compared to 30 volts
-Mark
I think it requires at least two of the iron core microwave oven units to get enough amperage, and it's getting harder to find those larger scrap ovens
If you have an old arc welder you can sacrifice, that would work- change the secondary winding
Click to expand...
Any ideas as to when these new ferrite transformers started being used? So most any OLD microwave will still have the iron core transformers?
 
Mutt said:
So I see a alot of videos of people making good spot welders outta microwave transformers. I took a microwave apart today (Panasonic) and it had the most ridiculously cheap transformer I have ever seen. Not even sure how it even worked. It was mostly plastic and the fewest winding of I have ever seen. So my question is this

Since that AC transformer just loses it secondary windings and some 2/0 welding cable is just double wrapped it in it's place and the rest of the machine just hobbled together from scrap laying around, I got to thinking. Why wouldnt it be possible to just install a couple of tapered copper mig welding tips into the electrode and ground holders of a AC welding machine and just use the welding machine for the current? I mean, you could make some tongs outta steel and screw the tips into it for better control, but will this work, or will the welder short circuit or something? Or better yet, turn the tig welder on AC and be able to use the pulse (timer) function and the foot pedal or hand trigger for better control
Click to expand...

A spot welder typically has a very low voltage but thousands of amps. A stick welder wouldn't be able to supply sufficient amperage. I have a Miller spot welder that is rated at 1.5 kva. The secondary amperage is 4,500 amps. This is about 30x what a typical arc welder is capable of.
 
I think Panasonic introduced the inverter microwave around 20 years ago, so you have to go back a ways.
Usually, the iron core models are heavier though so that's one way to tell
-M
 
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