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microwave transformers

Discussion in 'Electronic Repair' started by geoff smith, May 26, 2007.

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  1. geoff smith

    geoff smith Guest

    Can anyone suggest an interesting use for microwave oven transformers .
    Regards Geoff.
     
  2. Meat Plow

    Meat Plow Guest

    Power for an Electric Chair?


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  3. 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.

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  4. James Sweet

    James Sweet Guest

    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.
     
  5. clifto

    clifto Guest

    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.
     
  6. Charles

    Charles Guest

    Ham radio enthusiasts use them in power supplies for high-power vacuum tube
    transmitters.
     
  7. 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
     
  8. Sjouke Burry

    Sjouke Burry Guest

    If you switch around the primary and secondary,
    you get a nice low voltage high current transformer.
    And suddenly its not dangerous anymore.
     
  9. Arfa Daily

    Arfa Daily Guest

    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
     
  10. mike

    mike Guest

    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
     
  11. Arfa Daily

    Arfa Daily Guest

    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
     
  12. Guest


    That leaves the mains supply connected directly to the fixing bolts,
    so there is a safety issue to work around there.

    Nuke transformers have lots of uses, just google on them. But theyre
    far from ideal power transformers in almost every respect, so arent as
    good as might first be expected. An arc welder seems to be the most
    practical option.


    NT
     
  13. Jim Yanik

    Jim Yanik Guest

    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.
     
  14. Guest

    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
     
  15. Arfa Daily

    Arfa Daily Guest

    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
     
  16. mike

    mike Guest

    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
     
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