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From: Bob Eld on 8 Jan 2010 15:22

"Jon Kirwan" <jonk(a)infinitefactors.org> wrote in message
news:onsek5lsq6n8kk58n2np4oog3bh7l9klsg(a)4ax.com...
> On Fri, 8 Jan 2010 09:41:04 -0800, "Bob Eld"
> <nsmontassoc(a)yahoo.com> wrote:
>
> >"Jon Kirwan" <jonk(a)infinitefactors.org> wrote in message
> >news:c4lek5lo97unsndl47n9q4te62aeuecfl3(a)4ax.com...
> >> On Fri, 8 Jan 2010 07:35:15 -0800, "Bob Eld"
> >> <nsmontassoc(a)yahoo.com> wrote:
> >>
> >> >Twentyfive Amps is insufficient for welding. You need from about 50
amps
> >to
> >> >200 amps or so depending on the heat requirements for the gauge you
are
> >> >welding.
> >> >
> >> >Six or eight ga. wire on the secondary? That's not consistent with
25
> >amps
> >> >which would only require 10 ga.
> >>
> >> I think the OP was saying that 25A "continuous" works well.
> >> But I think the OP also wrote that this was an "industrial
> >> furnace for melting test specimens," which may have supported
> >> discontinuous currents that were higher. At least, I can
> >> tentatively accept the idea.
> >
> >Agreed, but how much of a current overload is reasonable, 4 times? for
100
> >Amps out or something similar? Secondly where does the power come from?
120
> >VAC input is already over taxed. I can't imagine that one would expect to
> >get 80 Amps out of a 120 Volt wall socket on a 20 Amp breaker. In other
> >words this transformer sounds like a missmatch for welding. Too much
> >voltage, not enough current.
> >
> >> >If the transformer is designed to drive silicon carbide elements, it
> >should
> >> >have some form of current control or be a constant current trasformer.
> >> >
> >> >2500 Watt, 100lb transformer for operation on 120VAC? Something
doesn't
> >add
> >> >up. We need actual specs to answer your question.
> >>
> >> If the peak current it supports is more than 25A, the
> >> transformer rating might be higher. I don't know, so it's
> >> good to ask.
> >>
> >> But here's a 10kW transformer that weighs 130 lbs:
> >
> >10 kW, 130lbs sounds about right. Then shouldn't this 2500 Watt unit be
> >about 33lbs?
> ><snip>
>
> Did the OP say it was a 2500 watt unit? I may have missed
> it.
>
> Jon

He said 25 Amps and up to 100 Volts. Admittedly it's an arm waving kind of a
discussion that why I asked for name plate specs. But, 120 VAC input is a
dead giveaway that we are not talking about much power. Most single phase
small kilns and furnaces run on 240VAC on 50 or 70 Amp circuits.

BTW, for welding it would be better if the current and voltage were
reversed; i.e., 100 Amps @ 25 Volts.


From: Jon Kirwan on 8 Jan 2010 15:30
On Fri, 8 Jan 2010 12:22:24 -0800, "Bob Eld"
<nsmontassoc(a)yahoo.com> wrote:

>
>"Jon Kirwan" <jonk(a)infinitefactors.org> wrote in message
>news:onsek5lsq6n8kk58n2np4oog3bh7l9klsg(a)4ax.com...
>> On Fri, 8 Jan 2010 09:41:04 -0800, "Bob Eld"
>> <nsmontassoc(a)yahoo.com> wrote:
>>
>> >"Jon Kirwan" <jonk(a)infinitefactors.org> wrote in message
>> >news:c4lek5lo97unsndl47n9q4te62aeuecfl3(a)4ax.com...
>> >> On Fri, 8 Jan 2010 07:35:15 -0800, "Bob Eld"
>> >> <nsmontassoc(a)yahoo.com> wrote:
>> >>
>> >> >Twentyfive Amps is insufficient for welding. You need from about 50
>amps
>> >to
>> >> >200 amps or so depending on the heat requirements for the gauge you
>are
>> >> >welding.
>> >> >
>> >> >Six or eight ga. wire on the secondary? That's not consistent with
>25
>> >amps
>> >> >which would only require 10 ga.
>> >>
>> >> I think the OP was saying that 25A "continuous" works well.
>> >> But I think the OP also wrote that this was an "industrial
>> >> furnace for melting test specimens," which may have supported
>> >> discontinuous currents that were higher. At least, I can
>> >> tentatively accept the idea.
>> >
>> >Agreed, but how much of a current overload is reasonable, 4 times? for
>100
>> >Amps out or something similar? Secondly where does the power come from?
>120
>> >VAC input is already over taxed. I can't imagine that one would expect to
>> >get 80 Amps out of a 120 Volt wall socket on a 20 Amp breaker. In other
>> >words this transformer sounds like a missmatch for welding. Too much
>> >voltage, not enough current.
>> >
>> >> >If the transformer is designed to drive silicon carbide elements, it
>> >should
>> >> >have some form of current control or be a constant current trasformer.
>> >> >
>> >> >2500 Watt, 100lb transformer for operation on 120VAC? Something
>doesn't
>> >add
>> >> >up. We need actual specs to answer your question.
>> >>
>> >> If the peak current it supports is more than 25A, the
>> >> transformer rating might be higher. I don't know, so it's
>> >> good to ask.
>> >>
>> >> But here's a 10kW transformer that weighs 130 lbs:
>> >
>> >10 kW, 130lbs sounds about right. Then shouldn't this 2500 Watt unit be
>> >about 33lbs?
>> ><snip>
>>
>> Did the OP say it was a 2500 watt unit? I may have missed
>> it.
>>
>> Jon
>
>He said 25 Amps and up to 100 Volts. Admittedly it's an arm waving kind of a
>discussion that why I asked for name plate specs. But, 120 VAC input is a
>dead giveaway that we are not talking about much power. Most single phase
>small kilns and furnaces run on 240VAC on 50 or 70 Amp circuits.

The way I read the OP was that this was a repurposed unit,
now being used as a kiln -- but not designed at the outset as
one. Maybe I am the one who misunderstood, though.

>BTW, for welding it would be better if the current and voltage were
>reversed; i.e., 100 Amps @ 25 Volts.

Yes, I think you made that point abundantly clear. I have no
experience and no reason to doubt it, either.

Jon
From: Michael A. Terrell on 8 Jan 2010 17:43

Bob Eld wrote:
>
> "Jon Kirwan" <jonk(a)infinitefactors.org> wrote in message
> news:c4lek5lo97unsndl47n9q4te62aeuecfl3(a)4ax.com...
> > On Fri, 8 Jan 2010 07:35:15 -0800, "Bob Eld"
> > <nsmontassoc(a)yahoo.com> wrote:
> >
> > >Twentyfive Amps is insufficient for welding. You need from about 50 amps
> to
> > >200 amps or so depending on the heat requirements for the gauge you are
> > >welding.
> > >
> > >Six or eight ga. wire on the secondary? That's not consistent with 25
> amps
> > >which would only require 10 ga.
> >
> > I think the OP was saying that 25A "continuous" works well.
> > But I think the OP also wrote that this was an "industrial
> > furnace for melting test specimens," which may have supported
> > discontinuous currents that were higher. At least, I can
> > tentatively accept the idea.
>
> Agreed, but how much of a current overload is reasonable, 4 times? for 100
> Amps out or something similar? Secondly where does the power come from? 120
> VAC input is already over taxed. I can't imagine that one would expect to
> get 80 Amps out of a 120 Volt wall socket on a 20 Amp breaker. In other
> words this transformer sounds like a missmatch for welding. Too much
> voltage, not enough current.


What are the duty cycles?


--
Greed is the root of all eBay.
From: TerryKing on 9 Jan 2010 05:18
I bet you can use your transformer, at least for the job you're
talking about. I've used a variety of transformers for welding, and
many were not at all ideal..

What Might Work:

- Use small (say 1/16 or 5/64 ) CONTACT type rods only (Type 7014 I
think) . You can start/keep an arc much easier than with other types.
They work OK at 50 amps.

- You need approximately constant current, with a higher arc-starting
voltage. So, use as much secondary as has both large wire and puts out
40 to 80 volts no load.

- Control the arc current with 'stuff' in series with the primary. I
have used toaster elements, and those Edison screw base heating
elements used in old 'reflector' space heaters. Back before I HEARD
of binary I somehow figured out to use 3 switches with sets of toaster
elements: 1, 2, 4 elements gave me, Hey! Anything from 1 to 7! I
was a lot smarter in 1956 than I am now :-) This was on a bigger
rewound pole transformer, you probably only need something like the
resistance of a 1000 or 2000 watt 120V heater (total elements).

The voltage under load will be 25 or 30 volts, I think.

If this is REALLY a one-shot deal, use your jumper cables as welding
cables.

REALLY, REALLY use a REAL welding helmet! Don't ask me why I know...

And, tell us how it went, so someone else can find your info!

Regards, Terry King ..On the Red Sea at KAUST
terry(a)terryking.us

From: Bob Masta on 9 Jan 2010 09:04
On Sat, 9 Jan 2010 02:18:02 -0800 (PST), TerryKing
<terry(a)terryking.us> wrote:

>I bet you can use your transformer, at least for the job you're
>talking about. I've used a variety of transformers for welding, and
>many were not at all ideal..
>
>What Might Work:
>
>- Use small (say 1/16 or 5/64 ) CONTACT type rods only (Type 7014 I
>think) . You can start/keep an arc much easier than with other types.
>They work OK at 50 amps.
>
>- You need approximately constant current, with a higher arc-starting
>voltage. So, use as much secondary as has both large wire and puts out
>40 to 80 volts no load.
>
>- Control the arc current with 'stuff' in series with the primary. I
>have used toaster elements, and those Edison screw base heating
>elements used in old 'reflector' space heaters. Back before I HEARD
>of binary I somehow figured out to use 3 switches with sets of toaster
>elements: 1, 2, 4 elements gave me, Hey! Anything from 1 to 7! I
>was a lot smarter in 1956 than I am now :-) This was on a bigger
>rewound pole transformer, you probably only need something like the
>resistance of a 1000 or 2000 watt 120V heater (total elements).
>
>The voltage under load will be 25 or 30 volts, I think.
>
>If this is REALLY a one-shot deal, use your jumper cables as welding
>cables.
>
>REALLY, REALLY use a REAL welding helmet! Don't ask me why I know...
>
>And, tell us how it went, so someone else can find your info!
>
>Regards, Terry King ..On the Red Sea at KAUST
>terry(a)terryking.us
>

Thanks, Terry. Yep, I definitely plan to use a
REAL welding helmet, cables, clamp, and gloves.
I was hoping to use some simple series inductance
instead of resistance, but I do have some space
heaters around that could do in a pinch.

For the other respondents who wondered about
transformer kVA and current: The nameplate on the
transformer only has volts and cycles (it's from
the '40s or 50s), but the exterior furnace
nameplate says that the input at 2500 degrees F is
1.55 kVA.

I may have been off on the weight, but my point is
that cheapie stick welders have dinky transformers
by comparison. They run them at *much* more
current than what a conventional transformer would
be rated at for continuous use, because they
always have a "duty cycle" listed, typically in
the 15% range. So you would be able to weld only
1.5 minutes out of every 10.

I'm sure I could get a much higher duty cycle out
of this beast, but I have no need for that. My
main concern is to not keep popping breakers.

Best regards,


Bob Masta

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