> I am in need of a large DC choke and thinking about making one from a
> microwave oven transformer. It appears that the E's and I's of the core are
> not interleaved so all I need to do is cut the weld holding the core
> together and it should fall apart. Hopefully in just two pieces. Then I can
> strip out the windings, put my own winding on, and, most importantly,
> sandwich a spacer so I have a gap (I said this was a DC choke).
>
> Anyone here ever play with microwave oven transformers at this level and
> learned any hard lessons?
>
> Thanks, Bob
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

>
> Personally, no. But the internet is full of people that have taken out the
> secondary windings and wound on 2-3 turns of heavy wire to produce a spot
> welder.
> Google around a bit on DIY spot welder and I'm sure you find lots of people
> hacking up these transformers in interesting ways. Probably something
> relevant to be learned there.
>
>
> -Denny
>
> On Mon, Jul 13, 2020 at 9:23 AM Bob Blick <bobblickKILLspamoutlook.com> wrote:
>
> > I am in need of a large DC choke and thinking about making one from a
> > microwave oven transformer. It appears that the E's and I's of the core are
> > not interleaved so all I need to do is cut the weld holding the core
> > together and it should fall apart. Hopefully in just two pieces. Then I can
> > strip out the windings, put my own winding on, and, most importantly,
> > sandwich a spacer so I have a gap (I said this was a DC choke).
> >
> > Anyone here ever play with microwave oven transformers at this level and
> > learned any hard lessons?
> >
> > Thanks, Bob
> > --
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > View/change your membership options at
> > mailman.mit.edu/mailman/listinfo/piclist
> >
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> mailman.mit.edu/mailman/listinfo/piclist

> I am in need of a large DC choke and thinking about making one from a
> microwave oven transformer. It appears that the E's and I's of the core are
> not interleaved so all I need to do is cut the weld holding the core
> together and it should fall apart. Hopefully in just two pieces. Then I can
> strip out the windings, put my own winding on, and, most importantly,
> sandwich a spacer so I have a gap (I said this was a DC choke).
>
> Anyone here ever play with microwave oven transformers at this level and
> learned any hard lessons?
>
> Thanks, Bob

>
> Personally, no. But the internet is full of people that have taken out the
> secondary windings and wound on 2-3 turns of heavy wire to produce a spot
> welder.
> Google around a bit on DIY spot welder and I'm sure you find lots of people
> hacking up these transformers in interesting ways. Probably something
> relevant to be learned there.
>
>
> -Denny
>
> On Mon, Jul 13, 2020 at 9:23 AM Bob Blick  wrote:
>
> > I am in need of a large DC choke and thinking about making one from a
> > microwave oven transformer. It appears that the E's and I's of the core are
> > not interleaved so all I need to do is cut the weld holding the core
> > together and it should fall apart. Hopefully in just two pieces. Then I can
> > strip out the windings, put my own winding on, and, most importantly,
> > sandwich a spacer so I have a gap (I said this was a DC choke).
> >
> > Anyone here ever play with microwave oven transformers at this level and
> > learned any hard lessons?
> >
> > Thanks, Bob

> Yes, that's why I thought it might be relatively easy, assuming everything
> didn't fall apart when I cut through the welds. This guy seems to have
> achieved it:
> https://www.youtube.com/watch?v=rCqddXhoP4E
> Cheerful regards, Bob
>
> ________________________________________
> From: RemoveMEpiclist-bouncesTakeThisOuTmit.edu <spamBeGonepiclist-bouncesspamBeGonemit.edu> on behalf of Alan
> Pearce
> Sent: Monday, July 13, 2020 12:51 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> I would have thought that a DC choke would not want the E and I
> laminations interleaved, rather an air gap to limit saturation of the
> core.
>
> On Mon, 13 Jul 2020 at 18:39, Denny Esterline  wrote:
> >
> > Personally, no. But the internet is full of people that have taken out
> the
> > secondary windings and wound on 2-3 turns of heavy wire to produce a spot
> > welder.
> > Google around a bit on DIY spot welder and I'm sure you find lots of
> people
> > hacking up these transformers in interesting ways. Probably something
> > relevant to be learned there.
> >
> >
> > -Denny
> >
> > On Mon, Jul 13, 2020 at 9:23 AM Bob Blick  wrote:
> >
> > > I am in need of a large DC choke and thinking about making one from a
> > > microwave oven transformer. It appears that the E's and I's of the
> core are
> > > not interleaved so all I need to do is cut the weld holding the core
> > > together and it should fall apart. Hopefully in just two pieces. Then
> I can
> > > strip out the windings, put my own winding on, and, most importantly,
> > > sandwich a spacer so I have a gap (I said this was a DC choke).
> > >
> > > Anyone here ever play with microwave oven transformers at this level
> and
> > > learned any hard lessons?
> > >
> > > Thanks, Bob
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

> Yes, that's why I thought it might be relatively easy, assuming everything
> didn't fall apart when I cut through the welds. This guy seems to have
> achieved it:
> https://www.youtube.com/watch?v=rCqddXhoP4E
> Cheerful regards, Bob
>
> ________________________________________
> From: piclist-bouncesEraseME.....mit.edu <EraseMEpiclist-bouncesmit.edu> on behalf of Alan
> Pearce
> Sent: Monday, July 13, 2020 12:51 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> I would have thought that a DC choke would not want the E and I
> laminations interleaved, rather an air gap to limit saturation of the
> core.
>
> On Mon, 13 Jul 2020 at 18:39, Denny Esterline  wrote:
> >
> > Personally, no. But the internet is full of people that have taken out
> the
> > secondary windings and wound on 2-3 turns of heavy wire to produce a spot
> > welder.
> > Google around a bit on DIY spot welder and I'm sure you find lots of
> people
> > hacking up these transformers in interesting ways. Probably something
> > relevant to be learned there.
> >
> >
> > -Denny
> >
> > On Mon, Jul 13, 2020 at 9:23 AM Bob Blick  wrote:
> >
> > > I am in need of a large DC choke and thinking about making one from a
> > > microwave oven transformer. It appears that the E's and I's of the
> core are
> > > not interleaved so all I need to do is cut the weld holding the core
> > > together and it should fall apart. Hopefully in just two pieces. Then
> I can
> > > strip out the windings, put my own winding on, and, most importantly,
> > > sandwich a spacer so I have a gap (I said this was a DC choke).
> > >
> > > Anyone here ever play with microwave oven transformers at this level
> and
> > > learned any hard lessons?
> > >
> > > Thanks, Bob

> That's pretty nice! I guess I shouldn't give up on finding a source for
> enameled wire. I will start with my current plan and see how much
> inductance I get, since I have lots of house wire.
> Thanks, Bob
>
> ________________________________________
> From: spamBeGonepiclist-bouncesSTOPspamEraseMEmit.edu <KILLspampiclist-bouncesspamBeGonemit.edu> on behalf of
> sergio
> Sent: Wednesday, July 15, 2020 10:13 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> https://www.wires.co.uk/acatalog/TX_3000-5000.html
>
> On Wed, 15 Jul 2020, Bob Blick wrote:
>
> > I know the insulation of house wire will waste as much space as the
> copper, but that's the way it is. It's hard to find thick enameled wire,
> and it would be very hard to wind 8AWG or thicker wire.
>
> A good place for wire:
>
> https://www.wires.co.uk/acatalog/TX_3000-5000.html
>
> They used to do much more so I guess they can get hold of a lot more than
> they advertise.
>
> Best Regards
> Sergio
> -
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

>
> Hi Graham,
>
> The choke is only going to be used at low voltage so you're right, I don't need to worry too much about insulation.
>
> I could strip off the insulation and bundle the four strands together before insulating. It would be rather stiff, but I've got tough fingers. Would use a lot of polyimide tape, I expect it to be about 30 turns. The widest I have is 30mm I think.
>
> Varnishing it is an interesting thought. I've got no experience with varnish or shellac, so finding something that would work from my local hardware store will be an interesting experiment.
>
> I have some 8AWH battery cable too. But probably not enough.
>
> Thanks for the ideas!
>
> Bob
> ________________________________________
> From: .....piclist-bouncesspam_OUTmit.edu <TakeThisOuTpiclist-bounces.....TakeThisOuTmit.edu> on behalf of graham foulkes
> Sent: Wednesday, July 15, 2020 10:57 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> HI
> 120 amp windings at low voltage, you don't need thick insulation on the
> wire. Maybe strip off the house cable insulation and lap wind with thin
> tape, electronic polyamide high temperature tape preferrably. I have used
> thin cotton tape to insulate scondary coils in a home built welder, still
> running 30 years later.
> Shellac lacquer is also an alternative, does not soften much with
> temperature increase and has good dielectric properties. Avoid PVC
> electrical tape, softens too easily and punctures when winding, stretches
> and so thins out.
>
> On Wed, Jul 15, 2020, 7:38 AM Bob Blick  wrote:
>
> > That's pretty nice! I guess I shouldn't give up on finding a source for
> > enameled wire. I will start with my current plan and see how much
> > inductance I get, since I have lots of house wire.
> > Thanks, Bob
> >
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> mailman.mit.edu/mailman/listinfo/piclist

>
> That makes a lot of sense. 12AWG wire is 2.05 mm diameter. The winding space is 45mm by 15mm. Maybe I can get 5 quad turns per layer by 6 layers or 4+ turns per layer and 7 layers for 30 total turns. If I am lucky, perhaps a few more.
>
> Stretching the wire ahead of time so it's straight and binds tightly together would be good to do. I can make a couple of wooden(or 3D printed) channels to hold the wires flat and together while I tape them, and slide them along as I tape.
>
> Thanks, Bob
>
> ________________________________________
> From: spamBeGonepiclist-bounces@spam@spam_OUTmit.edu <TakeThisOuTpiclist-bouncesspammit.edu> on behalf of Alan Pearce
> Sent: Wednesday, July 15, 2020 12:16 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> Rather than bundle the wire together before binding it I would try to
> lay the four lots side by side and then bind it so it is a flat wide
> strip. This will make it easier to wind on the core.
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> mailman.mit.edu/mailman/listinfo/piclist

> Just a quick update.
>
> Cutting apart the transformer was easy. Hacksawing along the two welds a
> little more than a millimeter deep was enough.
>
> Making my own flat wire is a bit challenging. I experimented on a 1 meter
> length. Stretching 12AWG solid wire to make it straight is hard. I will use
> a lever or other human invention. Keeping four 8-meter wires parallel while
> taping will be challenging. I may tack-solder it at intervals along its
> length. Spiral wrapping the Kapton tape seems to be easier than lengthwise.
>
> In the meantime, a friend gave me a transformer he had stripped the
> secondary from(in anticipation of making a spot welder) and then abandoned.
> I decided to do some tests just for giggles. It is a 120V 60Hz model, from
> an oven rated either 900 or 1000 watts. I connected it to a Variac and a
> low-quality AC volt/ammeter on the primary, wound 5 turns of 12AWG for a
> secondary, and put an RMS voltmeter and oscilloscope on it.
>
> Applying up to about 90 volts, primary current was 0.8A and I got
> something resembling a sine wave on the secondary, about 4.2V.
>
> By the time I got to 120V the primary current was 5.8A, there was minor
> annoying hum and the output waveform looked rather stressed-out 5.3V. See
> attached photo. 2V/division.
>
> The transformer still had its shunt blocks(search the internet and you
> will see what they look like and where they go). Removing them and
> retracing my steps gave me similar results at lower voltages but less
> voltage compression and 6.8A input current with 120V in. At 117V the
> current was 5.8A and output voltage was 5.27V
>
> Very little heat was produced, it appears that most power was reactive.
>
> More fun to follow some other day. I need to fix my chainsaw and do other
> important chores.
>
> Bob

> By the way, none of this is unexpected. The flux density in a transformer core is highest with no load, but microwave ovens are always running at full load, so they get along with fewer turns of wire and smaller cores than they would otherwise. They also don't interleave the laminations, which probably allows them to get away with an even smaller core at the expense of poorer regulation, which they also don't need.
>
> Adding 20 percent to the primary (about 20 more turns in this case) to the primary would probably allow it to work lots better at 120V. But at the expense of less room for a secondary winding, and less power.
>
> The moral of the story is that a microwave oven transformer works pretty well in a microwave oven.
>
> From: @spam@piclist-bouncesspam_OUT.....mit.edu spamBeGonepiclist-bouncesEraseMEmit.edu on behalf of Bob Blick
>
> Sent: Saturday, July 18, 2020 3:44 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> Just a quick update.
>
> Cutting apart the transformer was easy. Hacksawing along the two welds a little more than a millimeter deep was enough.
>
> Making my own flat wire is a bit challenging. I experimented on a 1 meter length. Stretching 12AWG solid wire to make it straight is hard. I will use a lever or other human invention. Keeping four 8-meter wires parallel while taping will be challenging. I may tack-solder it at intervals along its length. Spiral wrapping the Kapton tape seems to be easier than lengthwise.
>
> In the meantime, a friend gave me a transformer he had stripped the secondary from(in anticipation of making a spot welder) and then abandoned. I decided to do some tests just for giggles. It is a 120V 60Hz model, from an oven rated either 900 or 1000 watts. I connected it to a Variac and a low-quality AC volt/ammeter on the primary, wound 5 turns of 12AWG for a secondary, and put an RMS voltmeter and oscilloscope on it.
>
> Applying up to about 90 volts, primary current was 0.8A and I got something resembling a sine wave on the secondary, about 4.2V.
>
> By the time I got to 120V the primary current was 5.8A, there was minor annoying hum and the output waveform looked rather stressed-out 5.3V. See attached photo. 2V/division.
>
> The transformer still had its shunt blocks(search the internet and you will see what they look like and where they go). Removing them and retracing my steps gave me similar results at lower voltages but less voltage compression and 6.8A input current with 120V in. At 117V the current was 5.8A and output voltage was 5.27V
>
> Very little heat was produced, it appears that most power was reactive.
>
> More fun to follow some other day. I need to fix my chainsaw and do other important chores.
>
> Bob
>
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> By the way, none of this is unexpected. The flux density in a transformer core is highest with no load, but microwave ovens are always running at full load, so they get along with fewer turns of wire and smaller cores than they would otherwise. They also don't interleave the laminations, which probably allows them to get away with an even smaller core at the expense of poorer regulation, which they also don't need.
>
> Adding 20 percent to the primary (about 20 more turns in this case) to the primary would probably allow it to work lots better at 120V. But at the expense of less room for a secondary winding, and less power.
>
> The moral of the story is that a microwave oven transformer works pretty well in a microwave oven.
>
> From: .....piclist-bounces@spam@EraseMEmit.edu .....piclist-bouncesRemoveMEmit.edu on behalf of Bob Blick
>
> Sent: Saturday, July 18, 2020 3:44 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> Just a quick update.
>
> Cutting apart the transformer was easy. Hacksawing along the two welds a little more than a millimeter deep was enough.
>
> Making my own flat wire is a bit challenging. I experimented on a 1 meter length. Stretching 12AWG solid wire to make it straight is hard. I will use a lever or other human invention. Keeping four 8-meter wires parallel while taping will be challenging. I may tack-solder it at intervals along its length. Spiral wrapping the Kapton tape seems to be easier than lengthwise.
>
> In the meantime, a friend gave me a transformer he had stripped the secondary from(in anticipation of making a spot welder) and then abandoned. I decided to do some tests just for giggles. It is a 120V 60Hz model, from an oven rated either 900 or 1000 watts. I connected it to a Variac and a low-quality AC volt/ammeter on the primary, wound 5 turns of 12AWG for a secondary, and put an RMS voltmeter and oscilloscope on it.
>
> Applying up to about 90 volts, primary current was 0.8A and I got something resembling a sine wave on the secondary, about 4.2V.
>
> By the time I got to 120V the primary current was 5.8A, there was minor annoying hum and the output waveform looked rather stressed-out 5.3V. See attached photo. 2V/division.
>
> The transformer still had its shunt blocks(search the internet and you will see what they look like and where they go). Removing them and retracing my steps gave me similar results at lower voltages but less voltage compression and 6.8A input current with 120V in. At 117V the current was 5.8A and output voltage was 5.27V
>
> Very little heat was produced, it appears that most power was reactive.
>
> More fun to follow some other day. I need to fix my chainsaw and do other important chores.
>
> Bob
>
> -

> Quick update. Here's the almost finished inductor made from a microwave
> oven transformer. Right now with a gap of about 0.5 mm the inductance is
> about 1 millihenry. I will probably double to 1 mm which should lower the
> inductance by about 30 or 40 percent. Although I could weld it together as
> it was originally, I will just use the clamp as shown. The top plate is two
> pieces of wine barrel hoop butt welded together.
>
> Final number of turns is 25. Wire is 4 pieces of #12 AWG copper wire
> wrapped in more than 20 meters of 20mm wide polyimide tape.
>
> Hand and cat to show scale.
>
> Bob--
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

> Hi Ryan,
> I needed an inductor good for over 100 amps.
>
> One of my welders is a tiny thing as small as a lunch box. It's very
> convenient and efficient but doesn't like cellulosic electrodes, I want to
> see if adding inductance in series improves things. More likely, it will
> kill my welder after it kills the MOVs I add as protection :)
>
> There's very little real information available about why inverter-based
> welders usually don't work well with cellulosic electrodes. A lot of talk
> about open-circuit voltage not being high enough. That's clearly wrong,
> since the open-circuit voltage only affects the starting of the arc, and
> the problem here is the arc dying out. Cellulosic electrodes produce a lot
> of hydrogen, which does raise the arc voltage slightly, but it should be
> well within the welder's capability. I've run the welder on both 120 and
> 240 volts to see if that changes things, and it doesn't, which it would if
> the arc voltage was the problem. I think the real problem is the current
> limiting in the welder getting confused by the aggressive percussive arc
> that cellulosic rods produce.
>
> There is a whitepaper by ESAB(a welding equipment manufacturer) about the
> topic, and they suggest that inverter-based welders need large inductors in
> order to use cellulosic electrodes. So that fits in with my hypothesis.
>
> Even if it works out, the inductor probably won't become part of the
> welder, since it weighs as much as the whole welder. Just a little work
> avoidance exercise here in my little corner of the hobby-sphere.
>
> Friendly regards, Bob
>
> ________________________________________
> From: EraseMEpiclist-bouncesRemoveMESTOPspammit.edu <RemoveMEpiclist-bouncesKILLspamTakeThisOuTmit.edu> on behalf of Ryan
> O'Connor
> Sent: Wednesday, September 9, 2020 9:42 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> That's not many turns. What are you going to use it for?
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

> HI Bob
> There is a YouTube video, one of many about these Chinese inverter welders
> ,which addresses this issue of arc stability. It notes the poor arc strike
> capability at low current settings, no facts on electrode coatings, but
> similar solution, series inductor, which they miraculously cram into that
> miniature enclosure. They use, I think, a 30 mm powder iron toroid with a
> double layer wind of stranded wire.
> I bought two of these tiny welders, one 220 and a 120 volt version to see
> how well they perform. Not able to kill them so far!
> BTW, tyraps tend to stretch over time on stuff that warms up, good old
> fashioned cotton string works better, look at electric motor windings, they
> are always laced with twine.
>
> On Wed, Sep 9, 2020, 7:32 PM Bob Blick RemoveMEbobblickspam_OUToutlook.com wrote:
>
> > Hi Ryan,
> > I needed an inductor good for over 100 amps.
> > One of my welders is a tiny thing as small as a lunch box. It's very
> > convenient and efficient but doesn't like cellulosic electrodes, I want to
> > see if adding inductance in series improves things. More likely, it will
> > kill my welder after it kills the MOVs I add as protection :)
> > There's very little real information available about why inverter-based
> > welders usually don't work well with cellulosic electrodes. A lot of talk
> > about open-circuit voltage not being high enough. That's clearly wrong,
> > since the open-circuit voltage only affects the starting of the arc, and
> > the problem here is the arc dying out. Cellulosic electrodes produce a lot
> > of hydrogen, which does raise the arc voltage slightly, but it should be
> > well within the welder's capability. I've run the welder on both 120 and
> > 240 volts to see if that changes things, and it doesn't, which it would if
> > the arc voltage was the problem. I think the real problem is the current
> > limiting in the welder getting confused by the aggressive percussive arc
> > that cellulosic rods produce.
> > There is a whitepaper by ESAB(a welding equipment manufacturer) about the
> > topic, and they suggest that inverter-based welders need large inductors in
> > order to use cellulosic electrodes. So that fits in with my hypothesis.
> > Even if it works out, the inductor probably won't become part of the
> > welder, since it weighs as much as the whole welder. Just a little work
> > avoidance exercise here in my little corner of the hobby-sphere.
> > Friendly regards, Bob
> >
> > From: piclist-bouncesspammit.edu spam_OUTpiclist-bouncesspam_OUTspam_OUTmit.edu on behalf of Ryan
> > O'Connor
> > Sent: Wednesday, September 9, 2020 9:42 PM
> > To: Microcontroller discussion list - Public.
> > Subject: Re: [EE] Microwave Oven Transformers
> > That's not many turns. What are you going to use it for?
> > --
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> The MOVs will be at the output of the arc welder, before the inductor, to protect the welder's output rectifier. I plan to use three paralleled 20mm 360V MOVs(20D361K). By my cocktail napkin calculations, they should have no problem with the energy that they receive. It should not be a regularly occuring phenomena, I'm just naturally careful. I don't know what the welder uses for output rectifiers. They are fast recovery, not Schottky, but I don't know the voltage rating. I'm assuming they are at least 400V.
> Friendly regards, Bob
>
> From: KILLspampiclist-bouncesspamBeGonemit.edu piclist-bouncesspammit.edu on behalf of madscientistatlarge
>
> Sent: Thursday, September 10, 2020 9:29 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Microwave Oven Transformers
>
> I wouldn't put movs on it due to the energy levels and but gas discharge tubes would be nice. and hopefully could handle the load.
>
>
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

>
> Another quick update.
>
> To recap, this is a project to create a high current inductor to stabilize DC current up to about 100 Amps. I have an inexpensive lightweight lunchbox-size arc welder that works great with alkaline(6013) and low-hydrogen(7018) welding rods, but won't sustain an arc with cellulosic(6011) rods. My thought was to try adding inductance in series with the welding cables to hopefully allow use of cellulosic rods.
>
> My first attempt used a stripped microwave oven transformer with 25 turns of wire and a small air gap. Worked better with it than without it.
>
> I then tried using the inductor from my other arc welder, a Miller Thunderbolt AC/DC. Using that inductor, the little lunchbox welder burned 6011 rods "like butter", very smooth. The inductor from the Miller was very large, with a lot of turns of wire.
>
> I tore my microwave oven inductor apart and rewound it with about 52 turns of wire, reusing my wire. Previously I'd used 4 strands of 12AWG wire in parallel, but this time I used the same wire with only 2 strands in parallel. I also increased the air gap slightly.
>
> It works great, I can burn 6011 rods like nobody's business!
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> Pictures to follow in a week or so, time permitting. Who knows about heat and duty cycle, will know more as this project progresses.
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> Cheers! Bob