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microwave transformers

G

geoff smith

Can anyone suggest an interesting use for microwave oven transformers .
Regards Geoff.
 
M

Meat Plow

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

Power for an Electric Chair?


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S

Sam Goldwasser

geoff smith said:
Can anyone suggest an interesting use for microwave oven transformers .
Regards Geoff.

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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J

James Sweet

geoff smith said:
Can anyone suggest an interesting use for microwave oven transformers .
Regards Geoff.

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.
 
C

clifto

geoff said:
Can anyone suggest an interesting use for microwave oven transformers .

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.
 
C

Charles

geoff smith said:
Can anyone suggest an interesting use for microwave oven transformers .
Regards Geoff.

Ham radio enthusiasts use them in power supplies for high-power vacuum tube
transmitters.
 
M

Michael Black

geoff smith" ([email protected]) said:
Can anyone suggest an interesting use for microwave oven transformers .

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
 
S

Sjouke Burry

Charles said:
Ham radio enthusiasts use them in power supplies for high-power vacuum tube
transmitters.
If you switch around the primary and secondary,
you get a nice low voltage high current transformer.
And suddenly its not dangerous anymore.
 
A

Arfa Daily

Charles said:
Ham radio enthusiasts use them in power supplies for high-power vacuum
tube transmitters.
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
 
M

mike

Arfa said:
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
 
A

Arfa Daily

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


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
 
J

Jim Yanik

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

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.
 
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

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
 
A

Arfa Daily

Jim Yanik said:
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

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
 
M

mike

Arfa said:
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
 
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