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Sam

Fri Mar 24 2006, 11:57PM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

Hello everyone! It's the MOT freak, I have found an old '95 MO and the transformer in it bad, the secondary arc'd over to the core and BAM! there are lots of black marks and such... That must have scared the people using it. anyway I dont just want to throw it out, I wanna use it, it sucks as a ballast but I was thinking of rebuilding it. I know for sure its welded together but thats no big deal, I could use a hacksaw or something and then bolt it back together or go weld it up at my friends shop. I was wondering If I can use the priary alone and just redo the secondary for more voltage. I have nice 33g wire thats just begging to be used. what should I do? how do I? the things that I've found when searching are not alot of help.

Mike

Sat Mar 25 2006, 01:47AM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Hmm its possible to do this yes but it would be quite a pain, why not just find another Microwave oven transformer, they are so easy to get and it will take quite a while to unweld it, rew
ind it and then bolt it back together.

Sam

Sat Mar 25 2006, 02:15AM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

well in the time it took me to post this second message, I have unwelded 2 MO transformers and I think I'm gonna use the bigger one, I'll try to find my camera....

I was thinkiong maybe in the range for making a solid 1KW to 2KW TC with this thing.
I kept the 120 winding in very good condition but like expected the secondary is toast, It's a nice "EI" core and I still have the shunts. I called my friend and I can use his welder.

by the way I'm running on 60Hz and 120 is the best for me. mybe 220 but I hope not.
what is the best/highest voltage I can expect?

Sam

Sam

Sat Mar 25 2006, 02:23AM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

here are some pictures

Mike

Sat Mar 25 2006, 06:00AM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

oooh, cool, apparently its not as hard as I thought ;)

Good Luck!

vasil

Sat Mar 25 2006, 06:45AM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

I dont think u have much window on the core for big voltages. one idea is to make two secondaries in series each one for 2 kV (so 4 kV total), with a primary between them (like in a NST topology). it will be lower power too, because I dont think that you will have too much space for thicker wire.

Sam

Sat Mar 25 2006, 06:51AM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

yep! I got two of the suckers ripped apart. The first was a skill trainer, full of insolation and crap. the second was the neat xformer, neatly done in about 5 minutes.
Anyway I was thinking about the secondary, I could get 33gauge wire and alot!
How many turs should I put on this thing?
I wanna keep the pretty primary(hehe rhyme) but if it has to go it has to go. Do I need the metal shunts in there between the primary and secondary? what other things should I keep in mind?

ooooooh and whats the highest possible voltage with no oil? and I'm willing to coat in lots of clear coat....

vasil

Sat Mar 25 2006, 06:54AM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

It is hard to say, depends by the insulation of the outer turns of the secondary and the core arms. You have to run some calculus, calculate the secondary you need for the voltage you want, calculate the thickness of the secondary winding, compare with the window, decrease/increase the number of winding layers, etc...

your homework today

the_anomaly

Sat Mar 25 2006, 08:35AM

Registered Member #19 Joined: Thu Feb 02 2006, 03:19PM
Location: Jacksonville, FL
Posts: 168

I would leave the shunts in because without them you will end up drawing loads of power. Another quick way to open mots' is by using a dremel to cut along the weld of one side. When you have cut about 3mm deep take a flathead screwdriver and a hammer and chisel along that weld. The weld should pop open within the first few taps and then you can pry the mot from its base because the other sides weld will bend and break.

dan

Sat Mar 25 2006, 06:02PM

Registered Member #223 Joined: Mon Feb 20 2006, 06:42PM
Location: Ottawa, Ontario, Canada
Posts: 125

You can do away with the shunts if you want. This will give you more room for insulation and windings. I have removed the shunts from my MOTs in the past for more power. Also Pole pigs don't use shunts because they waste power. You will need an external ballast if you plan on shorting the secondary. I wouldn't really bother making a HV transformer out of a MOT core. There really isn't enough room in there for the ammount of insulation needed. Maybe under oil you might be able to make a 5kv-10kv transformer. But since you would need very fine wire to make the secondary fit I don't think you would get more than 200-500VA without overheating the secondary. Which is about the same as an NST anyway. MOTs can be rebuilt to make really good low voltage, high current transformers for welding or other LV,HC applications.

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