I just salvaged a transformer from a microwave and have a question about
the secondary windings . This one has 2 , one apparently a low voltage
since it has relatively few windings abt 6-10 , can't really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage or so .
The low voltage winding I can check with my voltmeter , but the HV winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and wonder
if someone has any idea of the voltage this winding might produce . I'm
pretty sure it's not in the KV range , but even a few hundred can totally
ruin your day ...

--
Snag

On 12/27/2014 8:25 PM, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a question about
the secondary windings . This one has 2 , one apparently a low voltage
since it has relatively few windings abt 6-10 , can't really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage or so .
The low voltage winding I can check with my voltmeter , but the HV winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and wonder
if someone has any idea of the voltage this winding might produce . I'm
pretty sure it's not in the KV range , but even a few hundred can totally
ruin your day ...

Ya, it could easily be 1000v.
A google search is needed.
ISTR they stick a voltage doubler on it and run around 2200Volts.

Mikek

On 2014-12-28, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a question about
the secondary windings . This one has 2 , one apparently a low voltage
since it has relatively few windings abt 6-10 , can't really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage or so .
The low voltage winding I can check with my voltmeter , but the HV winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and wonder
if someone has any idea of the voltage this winding might produce . I'm
pretty sure it's not in the KV range , but even a few hundred can totally
ruin your day ...

The low voltage part is to power the filament in the Klystron.

I would not be surprised if the HV side gets to 1KV or more,
frankly.

You can safely use an ohmmeter on it, as long as you aren't
powering the primary.

But why do you *care* about the secondaries. If you are going to
make a spot welder using it, you cut off the secondaries, and wind a few
turns of very heavy wire -- or even copper strap with insulation between
layers. You need *current*, not *voltage* for spot welding.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 12/27/2014 9:36 PM, amdx wrote:

Ya, it could easily be 1000v.
A google search is needed.
ISTR they stick a voltage doubler on it and run around 2200Volts.

I also remember 2000v, but I don't remember if that's before or after
the doubler. Either way, it's serious.

If you have a variac, put 5v on the primary & that should give 40 or 80v
or so on the secondary. If you really want to know.

Bob

On 12/27/2014 8:36 PM, amdx wrote:
On 12/27/2014 8:25 PM, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a question
about
the secondary windings . This one has 2 , one apparently a low voltage
since it has relatively few windings abt 6-10 , can't really tell of
16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage or
so .
The low voltage winding I can check with my voltmeter , but the HV
winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and
wonder
if someone has any idea of the voltage this winding might produce . I'm
pretty sure it's not in the KV range , but even a few hundred can totally
ruin your day ...

Ya, it could easily be 1000v.
A google search is needed.
ISTR they stick a voltage doubler on it and run around 2200Volts.

Mikek

I was wrong, it's about 2000 volts out.


http://www.kronjaeger.com/hv/hv/src/mot/

http://wiki.4hv.org/index.php/Microw...en_transformer

DoN. Nichols wrote:
On 2014-12-28, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a question
about the secondary windings . This one has 2 , one apparently a low
voltage since it has relatively few windings abt 6-10 , can't
really tell of 16 or 18 guage wire . The other a high voltage
winding of abt 28-30 guage or so . The low voltage winding I can
check with my voltmeter , but the HV winding I'm a bit leery of .
I'm not a big fan of getting electrocuted , and wonder if someone
has any idea of the voltage this winding might produce . I'm pretty
sure it's not in the KV range , but even a few hundred can totally
ruin your day ...

The low voltage part is to power the filament in the Klystron.

I would not be surprised if the HV side gets to 1KV or more,
frankly.

You can safely use an ohmmeter on it, as long as you aren't
powering the primary.

But why do you *care* about the secondaries. If you are going to
make a spot welder using it, you cut off the secondaries, and wind a
few turns of very heavy wire -- or even copper strap with insulation
between layers. You need *current*, not *voltage* for spot welding.

Good Luck,
DoN.

I have an inverter TIG machine that also does spot welds , or would if I
had the clamp fixture . I have no real plans for this MOT , but couldn't let
it go to the dump . I was mostly wondering if I was going to fry myself if I
powered this thing up . I'm surprised the voltage is that high , they used
plain stranded wire for the output leads . Obviously , I know very little
about microwaves - but that can be fixed .

--
Snag

DoN. Nichols formulated on Sunday :
On 2014-12-28, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a question about
the secondary windings . This one has 2 , one apparently a low voltage
since it has relatively few windings abt 6-10 , can't really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage or so .
The low voltage winding I can check with my voltmeter , but the HV winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and wonder
if someone has any idea of the voltage this winding might produce . I'm
pretty sure it's not in the KV range , but even a few hundred can totally
ruin your day ...

The low voltage part is to power the filament in the Klystron.

That Klystron is a magnetron and they are very different beasts.

I would not be surprised if the HV side gets to 1KV or more,
frankly.

You can safely use an ohmmeter on it, as long as you aren't
powering the primary.

But why do you *care* about the secondaries. If you are going to
make a spot welder using it, you cut off the secondaries, and wind a few
turns of very heavy wire -- or even copper strap with insulation between
layers. You need *current*, not *voltage* for spot welding.

Good Luck,
DoN.

--
John G Sydney.

amdx wrote:
On 12/27/2014 8:36 PM, amdx wrote:
On 12/27/2014 8:25 PM, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a
question about
the secondary windings . This one has 2 , one apparently a low
voltage since it has relatively few windings abt 6-10 , can't
really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage
or so .
The low voltage winding I can check with my voltmeter , but the HV
winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and
wonder
if someone has any idea of the voltage this winding might produce .
I'm pretty sure it's not in the KV range , but even a few hundred
can totally ruin your day ...

Ya, it could easily be 1000v.
A google search is needed.
ISTR they stick a voltage doubler on it and run around 2200Volts.

Mikek

I was wrong, it's about 2000 volts out.


http://www.kronjaeger.com/hv/hv/src/mot/

http://wiki.4hv.org/index.php/Microw...en_transformer

I don't think I'm going to be plugging it in ... I'm not equipped to deal
with those voltages safely . As I said in my reply to Don , I'm surprised
it's that high , they used plain stranded wire for output hookup wiring .

--
Snag

On Sat, 27 Dec 2014 20:25:59 -0600, "Terry Coombs"
wrote:

I just salvaged a transformer from a microwave and have a question about
the secondary windings . This one has 2 , one apparently a low voltage
since it has relatively few windings abt 6-10 , can't really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage or so .
The low voltage winding I can check with my voltmeter , but the HV winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and wonder
if someone has any idea of the voltage this winding might produce . I'm
pretty sure it's not in the KV range , but even a few hundred can totally
ruin your day ...
Generally a MOV secondary is in the 2KV range - at up ro 1700va -
definitely extremely dangerous.

On Sat, 27 Dec 2014 22:04:32 -0600, "Terry Coombs"
wrote:

amdx wrote:
On 12/27/2014 8:36 PM, amdx wrote:
On 12/27/2014 8:25 PM, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a
question about
the secondary windings . This one has 2 , one apparently a low
voltage since it has relatively few windings abt 6-10 , can't
really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage
or so .
The low voltage winding I can check with my voltmeter , but the HV
winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and
wonder
if someone has any idea of the voltage this winding might produce .
I'm pretty sure it's not in the KV range , but even a few hundred
can totally ruin your day ...

Ya, it could easily be 1000v.
A google search is needed.
ISTR they stick a voltage doubler on it and run around 2200Volts.

Mikek

I was wrong, it's about 2000 volts out.


http://www.kronjaeger.com/hv/hv/src/mot/

http://wiki.4hv.org/index.php/Microw...en_transformer

I don't think I'm going to be plugging it in ... I'm not equipped to deal
with those voltages safely . As I said in my reply to Don , I'm surprised
it's that high , they used plain stranded wire for output hookup wiring .
I had a transformer out od a very early B/W TV set as a kid. It had
all kinds of windings on it, from 1.5 volts IIRC to about 5000 volts.
The 5000 volts was at quite low current to drive the CRT. (Colout TVs
went up over 25000 volts)

I went for the low voltage winding at one end and got the high voltage
one instead - - - - - - - - - I lived. It was a dangerous piece of
equipment.

On Sat, 27 Dec 2014 23:29:35 -0500, wrote:

On Sat, 27 Dec 2014 22:04:32 -0600, "Terry Coombs"
wrote:

amdx wrote:
On 12/27/2014 8:36 PM, amdx wrote:
On 12/27/2014 8:25 PM, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a
question about
the secondary windings . This one has 2 , one apparently a low
voltage since it has relatively few windings abt 6-10 , can't
really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage
or so .
The low voltage winding I can check with my voltmeter , but the HV
winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and
wonder
if someone has any idea of the voltage this winding might produce .
I'm pretty sure it's not in the KV range , but even a few hundred
can totally ruin your day ...

Ya, it could easily be 1000v.
A google search is needed.
ISTR they stick a voltage doubler on it and run around 2200Volts.

Mikek

I was wrong, it's about 2000 volts out.


http://www.kronjaeger.com/hv/hv/src/mot/

http://wiki.4hv.org/index.php/Microw...en_transformer

I don't think I'm going to be plugging it in ... I'm not equipped to deal
with those voltages safely . As I said in my reply to Don , I'm surprised
it's that high , they used plain stranded wire for output hookup wiring .
I had a transformer out od a very early B/W TV set as a kid. It had
all kinds of windings on it, from 1.5 volts IIRC to about 5000 volts.
The 5000 volts was at quite low current to drive the CRT. (Colout TVs
went up over 25000 volts)

I went for the low voltage winding at one end and got the high voltage
one instead - - - - - - - - - I lived. It was a dangerous piece of
equipment.

Yeah, it's a good thing that those teensy little windings let so
little current through. The most I've been bit by is 800v from a b/w
TV chassis when troubleshooting at Coleman College. It left a bony
scar in the meat of my little fingertip for a decade.

Thank Crom for little miracles that we didn't run a crane into a
17-500kv line with hundreds of thousands of amps current possible.
Ever read the medical report on a guy who survived one of those? Too
gory for words. I'd rather die from that experience, truth be told.

--
Learn the art of patience. Apply discipline to your thoughts when they
become anxious over the outcome of a goal. Impatience breeds anxiety,
fear, discouragement and failure. Patience creates confidence, de-
cisiveness, and a rational outlook, which eventually leads to success.
--Brian Adams

On Sun, 28 Dec 2014 10:28:11 -0800, Larry Jaques
wrote:

On Sat, 27 Dec 2014 23:29:35 -0500, wrote:

On Sat, 27 Dec 2014 22:04:32 -0600, "Terry Coombs"
wrote:

amdx wrote:
On 12/27/2014 8:36 PM, amdx wrote:
On 12/27/2014 8:25 PM, Terry Coombs wrote:
I just salvaged a transformer from a microwave and have a
question about
the secondary windings . This one has 2 , one apparently a low
voltage since it has relatively few windings abt 6-10 , can't
really tell of 16 or
18 guage wire . The other a high voltage winding of abt 28-30 guage
or so .
The low voltage winding I can check with my voltmeter , but the HV
winding
I'm a bit leery of . I'm not a big fan of getting electrocuted , and
wonder
if someone has any idea of the voltage this winding might produce .
I'm pretty sure it's not in the KV range , but even a few hundred
can totally ruin your day ...

Ya, it could easily be 1000v.
A google search is needed.
ISTR they stick a voltage doubler on it and run around 2200Volts.

Mikek

I was wrong, it's about 2000 volts out.


http://www.kronjaeger.com/hv/hv/src/mot/

http://wiki.4hv.org/index.php/Microw...en_transformer

I don't think I'm going to be plugging it in ... I'm not equipped to deal
with those voltages safely . As I said in my reply to Don , I'm surprised
it's that high , they used plain stranded wire for output hookup wiring .
I had a transformer out od a very early B/W TV set as a kid. It had
all kinds of windings on it, from 1.5 volts IIRC to about 5000 volts.
The 5000 volts was at quite low current to drive the CRT. (Colout TVs
went up over 25000 volts)

I went for the low voltage winding at one end and got the high voltage
one instead - - - - - - - - - I lived. It was a dangerous piece of
equipment.

Yeah, it's a good thing that those teensy little windings let so
little current through. The most I've been bit by is 800v from a b/w
TV chassis when troubleshooting at Coleman College. It left a bony
scar in the meat of my little fingertip for a decade.

Thank Crom for little miracles that we didn't run a crane into a
17-500kv line with hundreds of thousands of amps current possible.
Ever read the medical report on a guy who survived one of those? Too
gory for words. I'd rather die from that experience, truth be told.

I know a guy who survived and lost the arm and leg on one side of his
body. He's in his early eighties now - artificial arm and leg.

On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on using 10 or larger wire and have a fairly high current low voltage transformer. This can be used to keep an exposed water pipe from freezing, or to apply a little heat to a water bowl for the animals.

Dan

On Sun, 28 Dec 2014 17:51:22 -0800 (PST), "
wrote:

On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on using 10 or larger wire and have a fairly high current low voltage transformer. This can be used to keep an exposed water pipe from freezing, or to apply a little heat to a water bowl for the animals.

Dan

I pulled one of those things out of a microwave once, and was startled
to see that the laminations were welded together in a strip.

What's up with that? I would have thought that the eddy currents would
be ferocious.

--
Ed Huntress

wrote:
On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on
using 10 or larger wire and have a fairly high current low voltage
transformer. This can be used to keep an exposed water pipe from
freezing, or to apply a little heat to a water bowl for the animals.

Dan

Do you think I could rewind the secondary for a power supply suitable for a
small inductive furnace ? I'd like the capability to melt small under 8 oz
quantities of brass/bronze alloys . My aluminum furnace is too big , I need
to build a smaller one and want to explore options - though I'll probably
end up using the propane burners I already have .

--
Snag

On 12/28/2014 9:22 PM, Terry Coombs wrote:
Do you think I could rewind the secondary for a power supply suitable for a
small inductive furnace ? I'd like the capability to melt small under 8 oz
quantities of brass/bronze alloys . My aluminum furnace is too big , I need
to build a smaller one and want to explore options - though I'll probably
end up using the propane burners I already have .


I don't know anything about inductive furnaces, but I have fooled around
with MOT's. I've always gotten about 1v per turn on the secondary. It
was surprising how consistent it was. The ones that I've had were about
1-1/2 kva, a common MO size. That doesn't seem like much power for
melting aluminum, but again, I don't know anything about inductive heating.

If you're going to be needing more than a few turns, I'd recommend
separating the E & I core sections - it makes the secondary removal and
adding the new winding so much easier.

Here's a write up of some of my fooling-arounds:
http://www.mwdropbox.com/dropbox/FunWithMOTs.pdf

Bob

On 12/28/2014 8:05 PM, Ed Huntress wrote:
On Sun, 28 Dec 2014 17:51:22 -0800 (PST), "
wrote:

On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on using 10 or larger wire and have a fairly high current low voltage transformer. This can be used to keep an exposed water pipe from freezing, or to apply a little heat to a water bowl for the animals.

Dan

I pulled one of those things out of a microwave once, and was startled
to see that the laminations were welded together in a strip.

What's up with that? I would have thought that the eddy currents would
be ferocious.

The strip type of laminations were very very high current. Some are in
the 10's of Amps with surges 100 Times.

Eddy currents depends on the alloy. I agree on the concept. I suspect
they were nominal to the real current.

The big 100 amp windings on soldering guns - where the posts that come
to the copper point are part of the winding like the copper point.
It suffers more from heat from the eddy and main current so the whole
gun heats up. But works for spot solders nicely.

Also tends to demagnetize if something is passed between the loop.

(Can make the solder a larger loop of 10 ga. copper - plastic on - for
that.)

Martin

In article , Ed Huntress
wrote:

On Sun, 28 Dec 2014 17:51:22 -0800 (PST), "
wrote:

On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on using
10 or larger wire and have a fairly high current low voltage transformer.
This can be used to keep an exposed water pipe from freezing, or to apply a
little heat to a water bowl for the animals.

Dan

I pulled one of those things out of a microwave once, and was startled
to see that the laminations were welded together in a strip.

What's up with that? I would have thought that the eddy currents would
be ferocious.

I don't visualize this, but can imagine how it would work. Silicon
steel has a fairly high resistivity, so if the eddy current paths are
long enough, the losses could be reasonable.

Joe Gwinn

On 12/28/2014 8:22 PM, Terry Coombs wrote:
wrote:
On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on
using 10 or larger wire and have a fairly high current low voltage
transformer. This can be used to keep an exposed water pipe from
freezing, or to apply a little heat to a water bowl for the animals.

Dan

Do you think I could rewind the secondary for a power supply suitable for a
small inductive furnace ? I'd like the capability to melt small under 8 oz
quantities of brass/bronze alloys . My aluminum furnace is too big , I need
to build a smaller one and want to explore options - though I'll probably
end up using the propane burners I already have .

Think of the power needed. The fist size transformers are 100 watts.
I think you would do well using a power pole transformer backwards for that!

Martin

Bob Engelhardt wrote:
On 12/28/2014 9:22 PM, Terry Coombs wrote:
Do you think I could rewind the secondary for a power supply
suitable for a small inductive furnace ? I'd like the capability to
melt small under 8 oz quantities of brass/bronze alloys . My
aluminum furnace is too big , I need to build a smaller one and want
to explore options - though I'll probably end up using the propane
burners I already have .

I don't know anything about inductive furnaces, but I have fooled
around with MOT's. I've always gotten about 1v per turn on the
secondary. It was surprising how consistent it was. The ones that
I've had were about 1-1/2 kva, a common MO size. That doesn't seem
like much power for melting aluminum, but again, I don't know
anything about inductive heating.
If you're going to be needing more than a few turns, I'd recommend
separating the E & I core sections - it makes the secondary removal
and adding the new winding so much easier.

Here's a write up of some of my fooling-arounds:
http://www.mwdropbox.com/dropbox/FunWithMOTs.pdf

Bob

Thanks Bob , that one volt/turn is a very useful piece of information . I
still have no particular use in mind , I just didn't want to toss it . Could
be the first piece to a power supply for a mill power feed ... Have power
regulators and necessary resistors/caps , need diodes . Dang , I knew I
shoulda grabbed my roll of 12ga primary wire too .

--
Snag

On Sun, 28 Dec 2014 21:05:05 -0500, Ed Huntress
wrote:

On Sun, 28 Dec 2014 17:51:22 -0800 (PST), "
wrote:

On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on using 10 or larger wire and have a fairly high current low voltage transformer. This can be used to keep an exposed water pipe from freezing, or to apply a little heat to a water bowl for the animals.

Dan

I pulled one of those things out of a microwave once, and was startled
to see that the laminations were welded together in a strip.

What's up with that? I would have thought that the eddy currents would
be ferocious.
They also tend to saturate badly when run at full voltage without a
load on the secondary.

On Sun, 28 Dec 2014 21:49:56 -0600, "Terry Coombs"
wrote:

Bob Engelhardt wrote:
On 12/28/2014 9:22 PM, Terry Coombs wrote:
Do you think I could rewind the secondary for a power supply
suitable for a small inductive furnace ? I'd like the capability to
melt small under 8 oz quantities of brass/bronze alloys . My
aluminum furnace is too big , I need to build a smaller one and want
to explore options - though I'll probably end up using the propane
burners I already have .

I don't know anything about inductive furnaces, but I have fooled
around with MOT's. I've always gotten about 1v per turn on the
secondary. It was surprising how consistent it was. The ones that
I've had were about 1-1/2 kva, a common MO size. That doesn't seem
like much power for melting aluminum, but again, I don't know
anything about inductive heating.
If you're going to be needing more than a few turns, I'd recommend
separating the E & I core sections - it makes the secondary removal
and adding the new winding so much easier.

Here's a write up of some of my fooling-arounds:
http://www.mwdropbox.com/dropbox/FunWithMOTs.pdf

Bob

Thanks Bob , that one volt/turn is a very useful piece of information . I
still have no particular use in mind , I just didn't want to toss it . Could
be the first piece to a power supply for a mill power feed ... Have power
regulators and necessary resistors/caps , need diodes . Dang , I knew I
shoulda grabbed my roll of 12ga primary wire too .
I separated 2 cores by grinding out the weld, and put 2 primaries on
one core to make an isolation transformer for working on old radios
like 5 tube ac/dc sets with "hot" chassis. I feed it from a large
Variac

On 12/28/2014 6:22 PM, Terry Coombs wrote:
wrote:
On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on
using 10 or larger wire and have a fairly high current low voltage
transformer. This can be used to keep an exposed water pipe from
freezing, or to apply a little heat to a water bowl for the animals.

I'd be interested in hearing more about this.
How do you keep the resistance of joints from concentrating
the heat in a small space with perhaps catastrophic results?

Dan

Do you think I could rewind the secondary for a power supply suitable for a
small inductive furnace ? I'd like the capability to melt small under 8 oz
quantities of brass/bronze alloys . My aluminum furnace is too big , I need
to build a smaller one and want to explore options - though I'll probably
end up using the propane burners I already have .

If you mean build a DC supply for your inductive furnace, probably.
But you still need the high frequency generator to produce the heat.

Older microwave transformers are designed to work more like current sources.
There are magnetic shunts that decrease the coupling between primary
and secondary. You can/should remove those shunts, but you're still
left with the fact that the vendor has no incentive to make a core
that achieves the tight coupling that you want in a typical transformer
application.

I'll second the saturation issue.
I built a battery tab spot welder around a two-turn secondary.
The weld consistency was horrible, so I gave up.
After I acquired my first digital storage scope and looked at the
waveforms, it was obvious that there was lots of hysteresis in the core
and the transformer was saturating.
I switched to multiple full-cycle pulses with start and stop at
line zero crossing, the weld consistency got much better.

On Sunday, December 28, 2014 9:05:18 PM UTC-5, Ed Huntress wrote:

I pulled one of those things out of a microwave once, and was startled
to see that the laminations were welded together in a strip.

What's up with that? I would have thought that the eddy currents would
be ferocious.

--
Ed Huntress

Did you visualize which way the eddy currents would go? The welds that hold the laminations together are fairly shallow and I believe the direction is orthogonal to the direction of the eddy currents.

Dan

On Sunday, December 28, 2014 9:22:50 PM UTC-5, Terry Coombs wrote:

Do you think I could rewind the secondary for a power supply suitable for a
small inductive furnace ? I'd like the capability to melt small under 8 oz
quantities of brass/bronze alloys . My aluminum furnace is too big , I need
to build a smaller one and want to explore options - though I'll probably
end up using the propane burners I already have .

--
Snag

I think inductive furnaces generally just rectify the line voltage and do not use a transformer for the power supply.

Dan

On Monday, December 29, 2014 5:25:58 AM UTC-5, mike wrote:

I'd be interested in hearing more about this.
How do you keep the resistance of joints from concentrating
the heat in a small space with perhaps catastrophic results?


You connect one end of the transformer secondary to one end of where the pipe is exposed to the weather, and the other end to the other end of the exposed pipe. Will work bost with iron pipe, but can work with copper pipe. Probably best to keep the magnetic shunt in the transformer.

Dan

On 2014-12-28, Larry Jaques wrote:
On Sat, 27 Dec 2014 23:29:35 -0500, wrote:

On Sat, 27 Dec 2014 22:04:32 -0600, "Terry Coombs"
wrote:

amdx wrote:

[ ... ]

I was wrong, it's about 2000 volts out.

[ ... ]

I had a transformer out od a very early B/W TV set as a kid. It had
all kinds of windings on it, from 1.5 volts IIRC to about 5000 volts.
The 5000 volts was at quite low current to drive the CRT. (Colout TVs
went up over 25000 volts)

I went for the low voltage winding at one end and got the high voltage
one instead - - - - - - - - - I lived. It was a dangerous piece of
equipment.

Yeah, it's a good thing that those teensy little windings let so
little current through. The most I've been bit by is 800v from a b/w
TV chassis when troubleshooting at Coleman College. It left a bony
scar in the meat of my little fingertip for a decade.

I got 2 KV from a power supply that could recharge a 200 uF bank
in 100 mS, so it was a serious zap.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 12/28/2014 8:22 PM, Terry Coombs wrote:
wrote:
On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on
using 10 or larger wire and have a fairly high current low voltage
transformer. This can be used to keep an exposed water pipe from
freezing, or to apply a little heat to a water bowl for the animals.

Dan

Do you think I could rewind the secondary for a power supply suitable for a
small inductive furnace ? I'd like the capability to melt small under 8 oz
quantities of brass/bronze alloys . My aluminum furnace is too big , I need
to build a smaller one and want to explore options - though I'll probably
end up using the propane burners I already have .


Sure, but I'm not sure you need it.
The input voltages vary all over, I see some at 12 Volts, 15 volts and
180 volts and one that just rectifies the line voltage for either 155
volts or 310 volts. Just pick a design that doesn't use a transformer.
http://www.seekic.com/circuit_diagra...ON_HEATER.html

The last time I was looking at one it was a kit, but the design was very
forgiving of the load, meaning he could change the work coil and still
get power to the piece being heated. So he could heat different size pieces.

Click on some of these, I'm sure you will find some neat designs and
videos of them in action.

Mikek

On 30 Dec 2014 00:46:07 GMT, "DoN. Nichols"
wrote:

On 2014-12-28, Larry Jaques wrote:
On Sat, 27 Dec 2014 23:29:35 -0500, wrote:

On Sat, 27 Dec 2014 22:04:32 -0600, "Terry Coombs"
wrote:

amdx wrote:

[ ... ]

I was wrong, it's about 2000 volts out.

[ ... ]

I had a transformer out od a very early B/W TV set as a kid. It had
all kinds of windings on it, from 1.5 volts IIRC to about 5000 volts.
The 5000 volts was at quite low current to drive the CRT. (Colout TVs
went up over 25000 volts)

I went for the low voltage winding at one end and got the high voltage
one instead - - - - - - - - - I lived. It was a dangerous piece of
equipment.

Yeah, it's a good thing that those teensy little windings let so
little current through. The most I've been bit by is 800v from a b/w
TV chassis when troubleshooting at Coleman College. It left a bony
scar in the meat of my little fingertip for a decade.

I got 2 KV from a power supply that could recharge a 200 uF bank
in 100 mS, so it was a serious zap.

Yes, that's a little more "real" than my measly 800v source.


I pulled apart two of my 3 spare ovens over the weekend. One had a
nice little xfmr, the other a plastic-cored, plastic-spooled coil of
8ga wire and semi-external ferrite rect. bar. I haven't pulled it
farther apart to see WTH the thing is, but any secondary winding is
hiding. http://diversifycomm.com/projects/

I hope the 3rd has a matching xfmr to the little one.

--
Poverty is easy. It's Charity and Chastity that are hard.
--anon

amdx wrote:
I wrote :
Do you think I could rewind the secondary for a power supply
suitable for a small inductive furnace ? I'd like the capability to
melt small under 8 oz quantities of brass/bronze alloys . My
aluminum furnace is too big , I need to build a smaller one and want
to explore options - though I'll probably end up using the propane
burners I already have .

Sure, but I'm not sure you need it.
The input voltages vary all over, I see some at 12 Volts, 15 volts
and 180 volts and one that just rectifies the line voltage for either
155 volts or 310 volts. Just pick a design that doesn't use a transformer.
http://www.seekic.com/circuit_diagra...ON_HEATER.html

The last time I was looking at one it was a kit, but the design was
very forgiving of the load, meaning he could change the work coil and
still get power to the piece being heated. So he could heat different size
pieces.
Click on some of these, I'm sure you will find some neat designs and
videos of them in action.

Mikek

I was just looking for a way to use this salvaged MOT , and I think I
found one . I need a multi-voltage power supply suitable for driving a small
stepper motor and other low-voltage DC devices . This was about a 900 watt
oven , I figger I can rewind multiple secondaries so they'll be
electrically isolated from each other , a necessity for some uses at
various voltages and rectify and control each separately . Got the
volt/current control devices and the necessary additional components , just
need some bridge rectifiers . This project is going on the back burner for
now , I got a table saw to repair so I can get my bee hives built for next
spring .

--
Snag

On 12/29/2014 9:37 PM, Larry Jaques wrote:
... I haven't pulled it
farther apart to see WTH the thing is, ...

Ahhh ... the latest MO technology: inverters. Just picking one up tells
all - the missing 5 lbs of steel and copper is obvious.

Larry Jaques wrote:

I pulled apart two of my 3 spare ovens over the weekend. One had a
nice little xfmr, the other a plastic-cored, plastic-spooled coil of
8ga wire and semi-external ferrite rect. bar. I haven't pulled it
farther apart to see WTH the thing is, but any secondary winding is
hiding. http://diversifycomm.com/projects/

I hope the 3rd has a matching xfmr to the little one.


Has anyone tried to modify a ballast from a street lamp? I picked up
five of them the other day, when a crew was rebuilding the lights in a
parking lot.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

On Wed, 31 Dec 2014 06:06:47 -0500, "Michael A. Terrell"
wrote:


Larry Jaques wrote:

I pulled apart two of my 3 spare ovens over the weekend. One had a
nice little xfmr, the other a plastic-cored, plastic-spooled coil of
8ga wire and semi-external ferrite rect. bar. I haven't pulled it
farther apart to see WTH the thing is, but any secondary winding is
hiding. http://diversifycomm.com/projects/

I hope the 3rd has a matching xfmr to the little one.

Has anyone tried to modify a ballast from a street lamp? I picked up
five of them the other day, when a crew was rebuilding the lights in a
parking lot.

Negatory here. Are they replacing them with LEDs and drivers?

On the local scene:
I pulled the last MOT out of the largest microwave oven and was really
surprised. www.diversifycomm.com/projects/MOTbigass.jpg I may not
need a pair of these guys after all. I have .8 x .94 holes after
getting the secondary winding out of the way. After hacksawing most
of the way through the first half, I chiseled the rest plus the other
side. It went much more quickly and smoothly. I'll do that to remove
xfmr windings in the future. The best chisel turned out to be an old
SnatchOn gasket scraper. g

--
Poverty is easy. It's Charity and Chastity that are hard.
--anon

On 12/31/2014 09:20 AM, Larry Jaques wrote:

On the local scene:
I pulled the last MOT out of the largest microwave oven and was really
surprised. www.diversifycomm.com/projects/MOTbigass.jpg I may not
need a pair of these guys after all. I have .8 x .94 holes after
getting the secondary winding out of the way. After hacksawing most
of the way through the first half, I chiseled the rest plus the other
side. It went much more quickly and smoothly. I'll do that to remove
xfmr windings in the future. The best chisel turned out to be an old
SnatchOn gasket scraper. g

I can't really tell from the picture, but it looks like one of the nice
ones I used to pull from the old faux-woodgrain ovens. The biggest ones
I ever harvested, two of them, were from old Sharp ovens, with a
mechanical bell and an analog timer. The trannies from those ovens had
laminations that were bolted together, instead of just having a weld
seam to hold them together. Big beefy suckers, and heavy as hell.

Jon

Bob Engelhardt wrote:
On 12/28/2014 9:22 PM, Terry Coombs wrote:
Do you think I could rewind the secondary for a power supply suitable for a
small inductive furnace ? I'd like the capability to melt small under 8 oz
quantities of brass/bronze alloys . My aluminum furnace is too big , I need
to build a smaller one and want to explore options - though I'll probably
end up using the propane burners I already have .


I don't know anything about inductive furnaces, but I have fooled around
with MOT's. I've always gotten about 1v per turn on the secondary. It
was surprising how consistent it was. The ones that I've had were about
1-1/2 kva, a common MO size. That doesn't seem like much power for
melting aluminum, but again, I don't know anything about inductive heating.

If you're going to be needing more than a few turns, I'd recommend
separating the E & I core sections - it makes the secondary removal and
adding the new winding so much easier.

Here's a write up of some of my fooling-arounds:
http://www.mwdropbox.com/dropbox/FunWithMOTs.pdf

I didn't know you could easily grind out the welded parts and not mess up
the laminations. Will have to try this.

On Saturday, January 3, 2015 1:19:27 AM UTC-5, Cydrome Leader wrote:


I didn't know you could easily grind out the welded parts and not mess up
the laminations. Will have to try this.

I think the welding is electro beam welding. I have cut out the welds on a MOT with a hacksaw

Dan.

wrote:
On Saturday, January 3, 2015 1:19:27 AM UTC-5, Cydrome Leader wrote:


I didn't know you could easily grind out the welded parts and not
mess up the laminations. Will have to try this.

I think the welding is electro beam welding. I have cut out the
welds on a MOT with a hacksaw

Dan.

I looked at the one I have laying here and it looks like a few minutes
with a dremel or maybe the bandsaw and it'll come apart . If done carefully
the remaining weld will keep the laminations together . This one looks like
it was just TIG fused or maybe as you said electro beam or laser .
--
Snag

On 1/3/2015 7:24 AM, Terry Coombs wrote:
wrote:
On Saturday, January 3, 2015 1:19:27 AM UTC-5, Cydrome Leader wrote:


I didn't know you could easily grind out the welded parts and not
mess up the laminations. Will have to try this.

I think the welding is electro beam welding. I have cut out the
welds on a MOT with a hacksaw

Dan.

I looked at the one I have laying here and it looks like a few minutes
with a dremel or maybe the bandsaw and it'll come apart . If done carefully
the remaining weld will keep the laminations together . This one looks like
it was just TIG fused or maybe as you said electro beam or laser .

Microwave transformers are designed to do ONE thing very well and CHEAP.
Rescue microwave transformers have a couple of uses.
Existing high voltage winding where you don't need tight coupling.
New secondary of few turns of big wire where you don't need tight coupling.
Most other applications are a fantasy of using the wrong part for
the application.
Once you grind it apart, how the hell are you gonna get it back together?

On Saturday, January 3, 2015 10:23:18 AM UTC-5, Terry Coombs wrote:
wrote:
On Saturday, January 3, 2015 1:19:27 AM UTC-5, Cydrome Leader wrote:

I didn't know you could easily grind out the welded parts and not
mess up the laminations. Will have to try this.

I think the welding is electro beam welding. I have cut out the
welds on a MOT with a hacksaw
Dan.

I looked at the one I have laying here and it looks like a few minutes
with a dremel or maybe the bandsaw and it'll come apart.

in general, working with electronics is good if you have 20/20 vision. If you know anyone in the field, you might want to invite them over and let them help.

On 12/28/2014 7:51 PM, wrote:
On Saturday, December 27, 2014 10:58:00 PM UTC-5, Terry Coombs wrote:

.

I have no real plans for this MOT , but couldn't let
it go to the dump .

--
Snag

If you remove the secondary winding , you can put a new secondary on using 10 or larger wire and have a fairly high current low voltage transformer. This can be used to keep an exposed water pipe from freezing, or to apply a little heat to a water bowl for the animals.





I have a transformer core from an old tombstone welder

http://tinyurl.com/pxmxm8p

Probably 5 or 6 times bigger than a big MOT.
Been storing it for years, it needs a project,
but I don't know what.
It would make a heck of a spot welder.
Mikek


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