Transformer from a microwave oven

Engineer · 2005-10-22T22:40:19+00:00

Hi, all...This may seem an odd post but I'm an avid re-user and recycler of old and/or scrapped electronic stuff (especially tube equipment), so I hope all will be clear...I have just picked over the carcass of a dead microwave oven (free junk from a church sale) to get a thermal switch to repair our main unit, but that's another story...I pulled out all the usable bits (not many!) but also the power transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs, and is 120 VAC to a scary 1,925 VAC (measured off load.) The core has two magnetic shunts between the windings to give, I think, a degree of voltage regulation (I may be able to press or knock them out, but I've not tried yet.) The 120 volt primary resistance is about 0.3 ohm; the 2 KV secondary is 115 ohms.Can anyone think of something useful to do with this this transformer. All I can come up with is:1. Use two of them back to back as a bench isolation transformer (but watch the 2 KV floating around!)2. Use as the OPT for a weird single-ended tube amplifier with 3.8 Kohm plate impedance (rather low) to a 15 ohm speaker (forget about 8 ohm speakers - too low; also need to isolate the secondary from the frame (easy enough to do).)3. Use it with a voltage doubler or tripler for an electrostatic filter (would not fit inside most units so serious safety engineering required.) Much too big, though.4. Run it off a suitable battery and interrupter (NOT AC mains!) to power an electric fence.5. Use it as a choke in a tube power supply. I'm not sure of the secondary winding inductance or current rating. Again, isolate the secondary.6. Use to replace another failed one Do they ever fail?That's it. Thanks for all ideas.Cheers,Roger

Oct 22, 2005 27 Replies

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cbarn24050 20 years ago

It's simple, allmost all politicians started out as lawyers, they were trained not to do anything except make it as difficult as possible for anyone else to.

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Chris Jones 20 years ago

Thanks for the answer.

Copyright standards especially ones which are mandatory and expensive (just to look at, let alone comply with) make me very very upset. Anyone would think that our respective governments really do want us to import everything and never design anything ourselves. In fact I think this is probably the case. I do wonder why though.

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Engineer 20 years ago

Did that. Close to 3 amps no load at 120 VAC. Ugly!

(snip)

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Engineer 20 years ago

(snip)

Not with a 3 amp magnetizing current. So, PF about zero! But since you don't pay for it... Still ugly! Cheers, Roger

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John Popelish 20 years ago

(snip)

So you just have to run it with a 66 uF connected across it. ;-)

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Tim Williams 20 years ago

Guarantee you it's saturation. Add 10 or 20 turns in series (in phase ;) with the primary, that'll drop it down a bit. Or use a buck transformer to

100-110V.

Tim

-- Deep Fryer: a very philosophical monk. Website:

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Sjouke Burry 20 years ago

Why not use the transfomer in the reverse way. My magnetron failed and I now have one for 220V 2000V and if you hook up the secondary to your mains, you get a transformer which can deliver quite some amps at (in my case)20 volts. You will have NO problems with saturation then. Regards,S Burry.

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Tim Williams 20 years ago

Yep, works absolutely perfect, IF you don't mind a 20VA transformer that weighs 20 pounds! LOL

Tim

-- Deep Fryer: a very philosophical monk. Website:

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