Here is the spot welder I made, it started off as having a modified MOT transformer as the power source but ended up with the transformer out of a 140A CIG arc welder. Bigger is better, right!
Pic 1. Pulled the 140A CIG welder apart, hit the secondary coil with a grinder and rewired it with two lengths of 70mm2 cable as it gave me more room to do so, the voltage went up a bit as well compared to the microwave transformer, probably due to the longer length of cable wrapped around the core, and also the double layer of cable. I now get 4.68V out of each pair compared to the 3.05V out of the original setup. No idea what the amperage will be as I don't have an instrument that will measure that high. I left the hole that the choke originally fitted in as I might want to scale down the power if welding thinner stuff. I am still toying with the idea of fitting in another 2 sets of coils in there.
Pic 2. Originally was going to use a modified Microwave Oven transformer but decided it needed to be bigger, there is a big difference in size between the two transformers, this new one weighs in at 25.5Kg vs the MOT 8.5Kg. Bit disappointed in how CIG made this one, they used aluminium strips instead of copper for the secondary coils and also ally wire for the primary coil, definitely built to a price.
Pic 3. Removed the secondary coil made out of flat aluminium ribbon.
Pic 4. Rewired the secondary with 2 coils of 70mm square multi strand welding cable.
Pic 5. Turning the copper. The copper was a piece of 25mm square copper that I had lying around for about 5 years and never used it, so machined it down in the lathe.
Pic 1. Pulled the 140A CIG welder apart, hit the secondary coil with a grinder and rewired it with two lengths of 70mm2 cable as it gave me more room to do so, the voltage went up a bit as well compared to the microwave transformer, probably due to the longer length of cable wrapped around the core, and also the double layer of cable. I now get 4.68V out of each pair compared to the 3.05V out of the original setup. No idea what the amperage will be as I don't have an instrument that will measure that high. I left the hole that the choke originally fitted in as I might want to scale down the power if welding thinner stuff. I am still toying with the idea of fitting in another 2 sets of coils in there.
Pic 2. Originally was going to use a modified Microwave Oven transformer but decided it needed to be bigger, there is a big difference in size between the two transformers, this new one weighs in at 25.5Kg vs the MOT 8.5Kg. Bit disappointed in how CIG made this one, they used aluminium strips instead of copper for the secondary coils and also ally wire for the primary coil, definitely built to a price.
Pic 3. Removed the secondary coil made out of flat aluminium ribbon.
Pic 4. Rewired the secondary with 2 coils of 70mm square multi strand welding cable.
Pic 5. Turning the copper. The copper was a piece of 25mm square copper that I had lying around for about 5 years and never used it, so machined it down in the lathe.