microwave transformers

Power for an Electric Chair?

-- #1 Offishul Ruiner of Usenet, March 2007 #1 Usenet Asshole, March 2007 #1 Bartlo Pset, March 13-24 2007 #10 Most hated Usenetizen of all time #8 AUK Hate Machine Cog Pierre Salinger Memorial Hook, Line & Sinker, June 2004 COOSN-266-06-25794

There are a number of uses but keep in mind that an intact microwave oven transformer can be very lethal. It's capable of several kV at a good fraction of an AMP - or even more - of current.

--- sam | Sci.Electronics.Repair FAQ:

Repair | Main Table of Contents:

+Lasers | Sam's Laser FAQ: | Mirror Sites:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

A pair of them in series makes a heck of a Jacob's Ladder, they can also be used to power large Tesla coils, or rewound to provide high power at lower voltages for things like spot welding. The HV is capable of quite a lot of current so it's very dangerous, use extreme care when playing with these.

1. Shot put.
2. Party hat for geek parties.
3. Paperweight.
4. Attach to used garage door extension spring for musclebuilder's yo-yo.
5. Put in paper boat for bathtub Titanic reenactment.
6. Tie to bumper of pickup truck for redneck wedding.
7. Label one "uranium" and send to Iran to wreck their centrifuges.
8. See how many you can stack vertically before they fall.
9. Cover with Silly Putty, drop into Grand Canyon and see how many airliners you can take out.
10. Electric handshake buzzer.

--
We can't possibly imprison 300 million Americans for not paying their
taxes, so let's grant all of them amnesty NOW!

Only if you ask in the proper place.

This newsgroup is about the repair of electronic equipment. Your's is at least the third post today treating it like a general purpose newsgroup.

There is the whole sci.electronics.* hierarchy to ask such questions, and I can immediately think of at least two of them where the question would be infinitely more on-topic.

See Mark Zenier's guide to the hierachy at ftp://ftp.eskimo.com/u/m/mzenier/seguide9706.txt

Michael

Although they're not actually terribly good for this use, as their design makes them self-limiting by way of core saturation, as I understand it.

Arfa

Core saturation blows fuses. Don't think that's the mechanism going on here. But there are magnetic shunts that increase the leakage inductance and limit current. Take out the shunts for non-limited applications. mike

--
Return address is VALID!
Bunch-O-Stuff Forsale Here:
http://mike.liveline.de/sale.html

That's probably right. I was going to use one for obtaining the HT supply for a 3CX400 I think it was, that I used in a grounded grid linear for 2 metres some years back, but in the end I didn't after reading a very detailed article on why they were no good for the job. As I say, it's been some years now, and the presence of magnetic shunts may well be the main reason quoted - I don't remember for sure. But something about the core size or it's characteristics or something seems to keep coming to mind as being the quoted reason for the secondary regulation being very poor when the current demand is variable, as it would be when powering an amplifier being driven with an SSB exciter, as opposed to it's designed use of providing the HT for a magnetron power oscillator, whose current demand will be pretty much constant. Maybe that situation has changed now, with the recent introduction of true power-controlled microwave ovens, rather than the former on-off switching control to produce an average cooking power ?? Maybe the trannies from this generation of ovens are better suited to 'alternative' uses ?

Arfa

"Arfa Daily" wrote in news:Kvc6i.11207$ snipped-for-privacy@newsfe1-win.ntli.net:

Uh,the microwave magnetron is a vacuum TUBE just like any RF transmitting tube,just for a different frequency. I see no reason for having the xfmr core saturate for a MW oven.

--
Jim Yanik
jyanik
at
kua.net

The magnetic shunt means the output is effectively in series with inductance, which does regulation no favours. But I gather that can be removed somehow.

A bigger problem is the fact that theyre rated for max 15 minutes use with forced air cooling - no fan and they fry quicker. 2 in series should solve that.

The output being connected to the core means fun mounting them too.

NT

Agreed, but the point I was making Jim, is that a microwave oven is a high power CW oscillator. Most required ham radio use is for high power tube linears which are most likely to be used for SSB transmissions, where the current demand will swing from maybe as little as zero, to some maximum, depending on the class and exact configuration of the amp. There is something about the construction of the microwave oven transformer core - and it seems to be the consensus that this is the presence of magnetic shunts rather than any core saturation - that makes them inherently self current limiting, thus keeping the magnetron operating in spec.

I would accept though that there should be no problem using one of these for an RF amp intended for FM or any other constant carrier amplitude mode, where the current demand on the power supply, will be largely constant.

Arfa

Don't get too excited about the magnetic shunts. Grab a hammer and knock 'em out. But since the transformer is designed to have high leakage inductance, the core is made of lousy material and NO effort is made to have tight coupling. I made a battery tab spot welder outa one. Cut off the secondary and put two turns of 2/0. Typical weld was 6 cycles of 60 Hz. Transformer got hot pretty fast. Weld repeatability was poor.

mike

--
Return address is VALID!
Bunch-O-Stuff Forsale Here:
http://mike.liveline.de/sale.html