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Posted by Steven Saunderson on February 23, 2008, 11:24 pm
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Hi,
I have an old Abel 130 amp welder that grunts and groans when I set it
to 100 amps or more. The hum starts to sound distressed a bit like the
unpleasant edge to a sound when a speaker is overloaded. It does work
however so maybe this is okay.
The transformer has a sliding core for amps adjustment which I guess is
common practice. What does seem odd is that this laminated core has
bulged in the middle so the laminations are separated rather than being
close together. Does anyone know if this is right or wrong ? If it is
wrong then I might be able to dismantle the core and rebuild it.
Also, there is no sign of any thermal protection device. Does this mean
the windings will melt if I push it too hard or do transformers degrade
at high temperatures and make the device self-limiting ?
Thanks,
--
Steven
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Posted by RoyJ on February 24, 2008, 10:41 am
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The older sliding core units tend to get sloppy in their old age, they
will really vibrate at the high range. I have an old Airco unit where
the slides are plastic, run against the laminations, wear from the
vibration. Check yours to see if there are any tighteners, gibs, etc to
snug up the shunt. You might have to insert a thin strip of plastic to
reduce the clearance.
Most of these old units had no thermal protection, got by with an
abundance of copper. If you run it hot, it will smoke a bit, time to
take a coffee break. If you are watching carefully, the arc will get a
bit mushy as the resistance of the windings goes up.
Steven Saunderson wrote:
> Hi,
>
> I have an old Abel 130 amp welder that grunts and groans when I set it
> to 100 amps or more. The hum starts to sound distressed a bit like the
> unpleasant edge to a sound when a speaker is overloaded. It does work
> however so maybe this is okay.
>
> The transformer has a sliding core for amps adjustment which I guess is
> common practice. What does seem odd is that this laminated core has
> bulged in the middle so the laminations are separated rather than being
> close together. Does anyone know if this is right or wrong ? If it is
> wrong then I might be able to dismantle the core and rebuild it.
>
> Also, there is no sign of any thermal protection device. Does this mean
> the windings will melt if I push it too hard or do transformers degrade
> at high temperatures and make the device self-limiting ?
>
> Thanks,
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Posted by Steven Saunderson on February 24, 2008, 3:35 pm
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> The older sliding core units tend to get sloppy in their old age, they
> will really vibrate at the high range.
Thanks for the info; I will have another look at the core.
> Most of these old units had no thermal protection, got by with an
> abundance of copper. If you run it hot, it will smoke a bit, time to
> take a coffee break. If you are watching carefully, the arc will get a
> bit mushy as the resistance of the windings goes up.
I think I saw this mushy arc effect recently especially on test beads.
The bead would start well but after perhaps two inches the arc was much
harder to keep alive. I've never worried about the duty cycle because I
spend so much time removing my helmet and chipping slag but it looks
like I am overworking the welder.
--
Steven
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Posted by RoyJ on February 24, 2008, 3:51 pm
Please log in for more thread options The mushy feel can come from either hot rod or hot welder. What size
rod? What amp setting? Did the effect go away with a cold rod? (the
welder won't cool much in the time it takes to insert a new rod.
If the welder is 120 volts, I'd expect the low duty cycle. If it is 240,
I doubt if you are hitting the duty cycle that quickly.
How much does the unit weigh? Heavy implies lots of iron and copper.
Steven Saunderson wrote:
>
>> The older sliding core units tend to get sloppy in their old age, they
>> will really vibrate at the high range.
>
> Thanks for the info; I will have another look at the core.
>
>> Most of these old units had no thermal protection, got by with an
>> abundance of copper. If you run it hot, it will smoke a bit, time to
>> take a coffee break. If you are watching carefully, the arc will get a
>> bit mushy as the resistance of the windings goes up.
>
> I think I saw this mushy arc effect recently especially on test beads.
> The bead would start well but after perhaps two inches the arc was much
> harder to keep alive. I've never worried about the duty cycle because I
> spend so much time removing my helmet and chipping slag but it looks
> like I am overworking the welder.
>
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Posted by Steven Saunderson on February 25, 2008, 1:27 am
Please log in for more thread options
Hi Roy,
I checked the sliding core today and it looks like the laminations are
bent so the core is a tight fit in the slides. The slides are aluminium
with plastic backing. I cleaned the feedscrew and slides and checked
all connections. When welding today (3.2mm rod, 120 amps) everything
was the same as before so I presume all is okay.
> The mushy feel can come from either hot rod or hot welder. What size
> rod? What amp setting? Did the effect go away with a cold rod? (the
> welder won't cool much in the time it takes to insert a new rod.
I was laying 8" long test beads (1 rod per bead). The rods are 2.5mm
and the welder was set to 90 - 100 amps. Most beads started okay but
the arc became fragile fairly quickly. I was trying beads with 3.2mm
rods before (120 -130 amps) and was having trouble. It looked like the
flux wasn't melting and I was almost dragging the rod along the metal
just to keep the arc alive. All rods are 6013 and I was trying a new
brand. The case of the welder was warm but certainly not hot.
> If the welder is 120 volts, I'd expect the low duty cycle. If it is 240,
> I doubt if you are hitting the duty cycle that quickly.
>
> How much does the unit weigh? Heavy implies lots of iron and copper.
The welder is 240 volts with a 25% duty cycle at 125 amps and 100% at 55
amps. I estimate it weighs 30 - 40kg.
I am beginning to suspect the new rods I bought recently. After the
problem session I bought a different brand of rods which seemed better.
But the welder had had an hour to cool down. As I am inexperienced,
blaming rods is a cheap tactic so I've just (mid-post) done another
test. I was laying beads with the suspect 3.2mm rods at 120 amps for
about five minutes and only stopping to change rods and chip slag so the
duty cycle was about 75%. The first bead was okay but after that I had
to keep the rod end real close to the metal to keep the arc going.
Immediately after I used these five rods I tried an expensive rod (same
specs) and it worked well with a 3 - 4mm arc. It looks like I am a dumb
newbie addicted to expensive comsumer rods.
The welder case was only moderately warm after this. It looks like it
is an oldie but a goodie.
--
Steven
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>
> I have an old Abel 130 amp welder that grunts and groans when I set it
> to 100 amps or more. The hum starts to sound distressed a bit like the
> unpleasant edge to a sound when a speaker is overloaded. It does work
> however so maybe this is okay.
>
> The transformer has a sliding core for amps adjustment which I guess is
> common practice. What does seem odd is that this laminated core has
> bulged in the middle so the laminations are separated rather than being
> close together. Does anyone know if this is right or wrong ? If it is
> wrong then I might be able to dismantle the core and rebuild it.
>
> Also, there is no sign of any thermal protection device. Does this mean
> the windings will melt if I push it too hard or do transformers degrade
> at high temperatures and make the device self-limiting ?
>
> Thanks,