pwf had an idea to make a quick and dirty spot welder for a project that involves welding a lot of 4mm wire (let’s say, they want to build a lot of wire baskets).

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Three microwave oven transformers in parallel are used as a power source. 30 mm2 wire is used as the secondary winding.

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A solid state relay is used to switch the power on.

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Control electronics employ two potentiometers that set the length of pulse and times to repeat the pulse.

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A 12 mm diameter copper rod was used for the business end.

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Business end doing business

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There is a handle and a footswitch for the convenience of the operator.

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The welder works ok. It’s totally stupid to switch the inductive load on zero crossing, but there is going to be another post about that. Now we are using pulses of 25 to 55 AC cycles in length to weld 3-4 mm steel wire. It should be around 3kW of power in theory, we managed to measure 900A of current running through the secondary. For now we suspect the limiting factor to be the AC cable that is wimpy 2x1.5 mm2.

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