MOT question

I just salvaged a transformer from a microwave and have a question about
the secondary windings . This one has 2 , one apparently a low voltage
since it has relatively few windings
Reply to
Terry Coombs
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Ya, it could easily be 1000v. A google search is needed. ISTR they stick a voltage doubler on it and run around 2200Volts.
Mikek
Reply to
amdx
The low voltage part is to power the filament in the Klystron.
I would not be surprised if the HV side gets to 1KV or more, frankly.
You can safely use an ohmmeter on it, as long as you aren't powering the primary.
But why do you *care* about the secondaries. If you are going to make a spot welder using it, you cut off the secondaries, and wind a few turns of very heavy wire -- or even copper strap with insulation between layers. You need *current*, not *voltage* for spot welding.
Good Luck, DoN.
Reply to
DoN. Nichols
I also remember 2000v, but I don't remember if that's before or after the doubler. Either way, it's serious.
If you have a variac, put 5v on the primary & that should give 40 or 80v or so on the secondary. If you really want to know.
Bob
Reply to
Bob Engelhardt
I was wrong, it's about 2000 volts out.
Reply to
amdx
I have an inverter TIG machine that also does spot welds , or would if I had the clamp fixture . I have no real plans for this MOT , but couldn't let it go to the dump . I was mostly wondering if I was going to fry myself if I powered this thing up . I'm surprised the voltage is that high , they used plain stranded wire for the output leads . Obviously , I know very little about microwaves - but that can be fixed .
Reply to
Terry Coombs
That Klystron is a magnetron and they are very different beasts.
Reply to
John G
I don't think I'm going to be plugging it in ... I'm not equipped to deal with those voltages safely . As I said in my reply to Don , I'm surprised it's that high , they used plain stranded wire for output hookup wiring .
Reply to
Terry Coombs
Generally a MOV secondary is in the 2KV range - at up ro 1700va - definitely extremely dangerous.
Reply to
clare
I had a transformer out od a very early B/W TV set as a kid. It had all kinds of windings on it, from 1.5 volts IIRC to about 5000 volts. The 5000 volts was at quite low current to drive the CRT. (Colout TVs went up over 25000 volts)
I went for the low voltage winding at one end and got the high voltage one instead - - - - - - - - - I lived. It was a dangerous piece of equipment.
Reply to
clare
Yeah, it's a good thing that those teensy little windings let so little current through. The most I've been bit by is 800v from a b/w TV chassis when troubleshooting at Coleman College. It left a bony scar in the meat of my little fingertip for a decade.
Thank Crom for little miracles that we didn't run a crane into a 17-500kv line with hundreds of thousands of amps current possible. Ever read the medical report on a guy who survived one of those? Too gory for words. I'd rather die from that experience, truth be told.
Reply to
Larry Jaques
I know a guy who survived and lost the arm and leg on one side of his body. He's in his early eighties now - artificial arm and leg.
Reply to
clare
If you remove the secondary winding , you can put a new secondary on using 10 or larger wire and have a fairly high current low voltage transformer. This can be used to keep an exposed water pipe from freezing, or to apply a little heat to a water bowl for the animals.
Dan
Reply to
dcaster
I pulled one of those things out of a microwave once, and was startled to see that the laminations were welded together in a strip.
What's up with that? I would have thought that the eddy currents would be ferocious.
Reply to
Ed Huntress
Do you think I could rewind the secondary for a power supply suitable for a small inductive furnace ? I'd like the capability to melt small quantities of brass/bronze alloys . My aluminum furnace is too big , I need to build a smaller one and want to explore options - though I'll probably end up using the propane burners I already have .
Reply to
Terry Coombs
I don't know anything about inductive furnaces, but I have fooled around with MOT's. I've always gotten about 1v per turn on the secondary. It was surprising how consistent it was. The ones that I've had were about 1-1/2 kva, a common MO size. That doesn't seem like much power for melting aluminum, but again, I don't know anything about inductive heating.
If you're going to be needing more than a few turns, I'd recommend separating the E & I core sections - it makes the secondary removal and adding the new winding so much easier.
Here's a write up of some of my fooling-arounds:
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Bob
Reply to
Bob Engelhardt
The strip type of laminations were very very high current. Some are in the 10's of Amps with surges 100 Times.
Eddy currents depends on the alloy. I agree on the concept. I suspect they were nominal to the real current.
The big 100 amp windings on soldering guns - where the posts that come to the copper point are part of the winding like the copper point. It suffers more from heat from the eddy and main current so the whole gun heats up. But works for spot solders nicely.
Also tends to demagnetize if something is passed between the loop.
(Can make the solder a larger loop of 10 ga. copper - plastic on - for that.)
Martin
Reply to
Martin Eastburn
I don't visualize this, but can imagine how it would work. Silicon steel has a fairly high resistivity, so if the eddy current paths are long enough, the losses could be reasonable.
Joe Gwinn
Reply to
Joe Gwinn
Think of the power needed. The fist size transformers are 100 watts. I think you would do well using a power pole transformer backwards for that!
Martin
Reply to
Martin Eastburn
Thanks Bob , that one volt/turn is a very useful piece of information . I still have no particular use in mind , I just didn't want to toss it . Could be the first piece to a power supply for a mill power feed ... Have power regulators and necessary resistors/caps , need diodes . Dang , I knew I shoulda grabbed my roll of 12ga primary wire too .
Reply to
Terry Coombs

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