Gallery, Projects and General > The Design Shop
Microwave owen transformer spot welder?
PekkaNF:
Thanks.
Bill, my friend is fixing one old east german bandsaw blade welder and he got it working....problem is annealing cycle after the weld. Old transformer had leaked all smoke out. I gave him a small buzzbox welder and he sawed secondary out put there three (I think???) rounds of 95mm2 fine wire cable coaxed into soft shrink tube (all from local winding shop). It's almost finished.
I'll follow up the links&leads.
I'm still wondering the shunts between windings. Some instructions tell to leave them, but they "rob" part of the flux. i don't get it. Why they are good, unless you want to limit current....or maybe they are there to load the primary a little even when secondary is open circuit????
Pekka
vtsteam:
--- Quote from: BillTodd on November 17, 2015, 09:12:24 AM ---I've been playing around with a MW transformer making a bandsaw blade welder ( The butt weld mechanism has to be surprisingly accurate - so far I have made two good welds from several feet of blade :LOL: )
Initially, I tried using a spot welder to power the blade welder, but the spot welder is low voltage (~1.7vac - one turn with a 230v primary) .The blade welder needs two or three turns ( I've been experimenting with more but 2-3 seemed to work best)
--- End quote ---
That looks handy, Bill.
BillTodd:
--- Quote ---I'm still wondering the shunts between windings. Some instructions tell to leave them, but they "rob" part of the flux. i don't get it. Why they are good, unless you want to limit current....or maybe they are there to load the primary a little even when secondary is open circuit????
--- End quote ---
I took mine out to give more room for windings. I suspect the shunts are necessary in the original, to add inductance (the MW load is mainly capacitive, so might be require to limit current in secondary) .
PekkaNF:
Ineresting reading on shunts. Some nice anecdotes on magnetrons and radars.
Now I have to deside what to test next.
Pekka
Manxmodder:
--- Quote from: BillTodd on November 17, 2015, 09:12:24 AM ---I've been playing around with a MW transformer making a bandsaw blade welder ( The butt weld mechanism has to be surprisingly accurate - so far I have made two good welds from several feet of blade :LOL: )
Initially, I tried using a spot welder to power the blade welder, but the spot welder is low voltage (~1.7vac - one turn with a 230v primary) .The blade welder needs two or three turns ( I've been experimenting with more but 2-3 seemed to work best)
For a spot welder you'll need to mount the transformer as close to the jaws as possible to keep the resistance down. The current flow is huge: I measured way over 600A from a small hand-held spot welder.
Use the as much copper you can squeeze into the transformer gap (I'd use multiple strips lacquered or taped to insulate them ).
--- End quote ---
Not a specifically a spot welder but I do like Tom's techniques method and apparatus for silver soldering bandsaw blades.
Youtube video link:
...OZ.
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