Spot Welder with mobile tips and capacitor

Hi, this is my version of electric spot welder build from 800w microwave transformer. I not use any fan because  rele  active MOT transformer only 2~3 seconds at a time.

I use a second 24V transformer  for activate the rele by micro-switch because I dont like have 220V near my hands :)

I use capacitor that I not see to use from anyone and I dont know why .. this is the basic of electrotechnology for power factor correction systems inductive.
The capacitor depend of your transformer, I use 25mf, my cosfi is 0,6 and the real power consuption is 1400w. it is less, when I found other one I added it in parallel ... the target is ~50mF with cosfi near 0,9 equal at 800w real consuption.

The advantage of this is you use less power in input, you have more power in output and your transformer remain a bit cooler.

Some attention to the contact of Relè, with correct cosfi (0,9) the current on the primary coil is around 4 Amperes (8 Amp with 110V). If you not use a condenser the cosfi around 0,2~0,3 and primary current around 12A at 220V (24A at 110V).

In my case my cosfi is 0,6 and my primary current around 7A. Find relè with contact for this current is hardest, I use one I had, it has 3 contact each of 3A and connect in parallel for total of 9A.

 Secondary coil is made with 3 turn of wire that has ~7mm of diametre, I use industrial ground cable.
Advantage of use  rele is that you power on after  you have positioned the tips to prevent the corrosion and gluing of it  :)

At right, the test current ... 667 Amp ... ummm ..  so good : )   .. but when I correct my cosfi with add other condenser the current go up ... I suppose go up to 20~30%. If you have questions, post them below

These are the video on my youtube channel: build or scheme

The microwave transformer is easy to mod and have more wattage but if you want, you use other transformer like toroidal .. in this video see this when I use to repair my RC brushed motor ... basic of spot welder  .. :D