MOT hacking

alt.binaries.schematics.electronic,sci.electronics.design,sci.electronics.basics

I just tapped them out with a flat tip screw driver away from the primary winding. Comes out easy. Do keep us posted on your progress, my eye's are perked up!

Whaddya think yo better than me?

I use wood and a chisel or screwdriver and hammer... :-)

If you want to get the windings off I recommend (I probably did already) hacksawing or grinding the weld off the "I" section, then lightly bashing (can I use those two words together?) the primary off. Then you can glue up a bobbin from cardboard and slip your secondary on much easier. A clamp from the shop keeps the I firmly on the E until you feel like welding it back on or whatever.

Tim

Eek! I'm nowhere near that point yet. It seems that the wire I scrounged is somehow stiffer than I remember #18 hookup wire, but it's motor wire after all. The insulation has the look and feel of "Heavy Formvar" or "Polythermaleze" or something. I've threaded a few turns by just threading the wire through the winding window, and it looks like crap - that is, what I've got for a "winding" is kinda tangle-wound, but it turns out that because of the stiffness of the wire, and the toughness of the insulation, it's not all that bad threading it through the eyes, albeit time-consuming. The tangle-winding I have there now I'm sure would work electrically, but it looks like crap, and would probably buzz. So, I dedided, since I intend to show it off, it should look neat, so I've decided to 5-minute epoxy each winding into place as I go along; this should only take 2.5 hours to do 15 turns. ;-)

Cheers! Rich

Oh, and of course, don't forget the boredom medicine of your choice, ;-)

C! R

Golly, Rich, make your life easy, and grind the welds away, and take the center out of your tranny. Then you can wind the windings very neatly. You don't have to weld the center back, you can toss some of your 5 minute epoxy at it, and all will be well.

-Chuck

Doesn't the extra air gap cause problems?

I doubt it, those things saturate on the peaks anyway. L will be lower but Imax will be higher.

Tim

No, because you are only removing a small percentage of the lamination iron. If you are truly concerned, you can weld it back up.

-Chuck

Ok. I'd still avoid epoxy because it falls apart with heat. A resorcinol or urea glue would resist that.

Uh . . . the air gap is part of the way the/a magnetic shunt works - as the secondary draws more current than you want, the magnetic field is diverted into the shunt (bypasses the rest of the core and secondary). Bigger gap sets the current limit higher. Skewed gap gives a sloppy "knee" in the current limit.

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We weren't talking about the shunts. They are popped out. We were talking about opening the core so you can remove the bobbin and wind it easily.

-Chuck

Oh. MOT I'm using only had a weld on the shunt.

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This one, the shunts just popped out - tap, tap, tap, toink! But, since I'm having so much fun threading this wire through the EI eyes, epoxying each turn into place, I really don't feel like cutting up the core. I can see where it's welded, and I have access to all manner of grinders and a chop saw, and my office opens onto a weld shop, so it's theoretically doable, but I can thread wire sitting down. ;-) Plus, I don't want to introduce any new gaps - I'd rather change as little as possible per experiment. :-)

Thanks! Rich

I know you're having fun. What is the volts per turn? or turns per volt.

American Science and Surplus had some very inexpensive 1 KVA toroid isolation transformers awhile back They are 0.84 volts per turn - Brand new for ~$12 with flat rate shipping. But you can't beat MOT's for cost effective.

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Yup. Can't get much cheaper than free! ;-)

Cheers! Rich

Its a bit late for the u-wave oven you got the transformer from, but a handy tip for curing the problem of the lights keep blowing when people are a bit heavy handed shutting the door - watch out for CFLs with slim bodies and check if they fit the space available before hunting everywhere for the proper bulbs - CFLs seem to be a little more robust in this application!