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Voltage/current curves

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Re: Voltage/current curves

Postby WerkSpace » Wed Jan 21, 2015 10:51 pm

I collect old aircraft generators and they can be set up similar to the earlier engine driven welders.
http://www.api-assembled.com/design/tech/welder/welder.htm
Bill Beauregard wrote: As to how these machines change voltage I don't know. They have ranges of amperage, then fine control is done with voltage. At lower voltage arc length has more effect on voltage, therefore amperage. You are able to bury the electrode, melting lots of rod surrounded by cold steel preventing drips. As you used up substantial heat melting rod, less is dumped into the work piece. It freezes sooner.
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Re: Voltage/current curves

Postby wheresmejumper » Thu Jan 22, 2015 5:18 am

i think you are confusing OCV with working voltage
Open Circuit Voltage is whats present before an arc is struck,and only directly affects how easy a rod will strike up
crappy welders could be as low as 48v,good ones up to 115v ive seen
Working Voltage is whats present when actually welding.this is what gives the welder its characteristics with a particular rod.
20v with smaller welders which struggle with 6010 or 7018. 25v is average and lincoln pipeliners up to 40v









Some older welders have adjustable voltage. I've lost track of the exact model, Travis Field demonstrates setting a 1959 Lincoln SA200? As to how these machines change voltage I don't know. They have ranges of amperage, then fine control is done with voltage. At lower voltage arc length has more effect on voltage, therefore amperage. You are able to bury the electrode, melting lots of rod surrounded by cold steel preventing drips. As you used up substantial heat melting rod, less is dumped into the work piece. It freezes sooner.

As for Dynasty, I haven't found volt/amp curves.

Bobcat does show the graphs with varying voltage over a narrower range controlled by what, I don't know. These seem to average 25 volts. I once had a 1940s era Westinghouse 600 amp engine welder. OCV was 36 at highest voltage. You adjusted down from there. When I first used it, it was owned by my father's friend. He had hundreds of hours experience with it. With his settings, it was wonderful! It had a Chrysler industrial 236 flat head 25" engine. With no exhaust, the noise was life changing![/quote]
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Re: Voltage/current curves

Postby Bill Beauregard » Thu Jan 22, 2015 9:05 am

wheresmejumper wrote:i think you are confusing OCV with working voltage
Open Circuit Voltage is whats present before an arc is struck,and only directly affects how easy a rod will strike up
crappy welders could be as low as 48v,good ones up to 115v ive seen
Working Voltage is whats present when actually welding.this is what gives the welder its characteristics with a particular rod.
20v with smaller welders which struggle with 6010 or 7018. 25v is average and lincoln pipeliners up to 40v


Nope, crystal clear on OCV being different from welding voltage. I do know that in position welding you need watts. how they are provided is less critical. Higher voltage means lower amperage. Pipe welders aren't going to stop and readjust the machine as they move around the pipe. They need to prevent sag.






Some older welders have adjustable voltage. I've lost track of the exact model, Travis Field demonstrates setting a 1959 Lincoln SA200? As to how these machines change voltage I don't know. They have ranges of amperage, then fine control is done with voltage. At lower voltage arc length has more effect on voltage, therefore amperage. You are able to bury the electrode, melting lots of rod surrounded by cold steel preventing drips. As you used up substantial heat melting rod, less is dumped into the work piece. It freezes sooner.

As for Dynasty, I haven't found volt/amp curves.

Bobcat does show the graphs with varying voltage over a narrower range controlled by what, I don't know. These seem to average 25 volts. I once had a 1940s era Westinghouse 600 amp engine welder. OCV was 36 at highest voltage. You adjusted down from there. When I first used it, it was owned by my father's friend. He had hundreds of hours experience with it. With his settings, it was wonderful! It had a Chrysler industrial 236 flat head 25" engine. With no exhaust, the noise was life changing!
[/quote]
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Re: Voltage/current curves

Postby Bill Beauregard » Thu Jan 22, 2015 9:12 am

WerkSpace wrote:I collect old aircraft generators and they can be set up similar to the earlier engine driven welders.
http://www.api-assembled.com/design/tech/welder/welder.htm
Bill Beauregard wrote: As to how these machines change voltage I don't know. They have ranges of amperage, then fine control is done with voltage. At lower voltage arc length has more effect on voltage, therefore amperage. You are able to bury the electrode, melting lots of rod surrounded by cold steel preventing drips. As you used up substantial heat melting rod, less is dumped into the work piece. It freezes sooner.


I was referring to the Lincoln SA__ machines. I guess voltage is either controlled with the rheostat or engine throttle. Might amperage be a matter of varying inductance?
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Re: Voltage/current curves

Postby WerkSpace » Thu Jan 22, 2015 10:00 am

The rheostat is controlling the current thru the stator, which controls the voltage output.
It functions as a sort of Magnetic Amplifier. The regulator on your car alternator works in a similar fashion.
The field terminals on a car alternator determine the output.
As your battery arrives at near full charge, the regulator will adjust the voltage on the field and the alternator will reduce its output substantially.

Just for fun, try this simple experiment. If you have a desk lamp that uses a small transformer to reduce the line voltage to the lamp's 12 volt bulb, place a permanent magnet next to the transformer. You will notice that you are able to control the 12 volt bulb's brightness by moving the magnet closer or farther away. This is because the transformer cannot reach magnetic saturation, so the secondary coil of the transformer has no way of producing current. Transformers can only function with expanding and collapsing magnetic fields. If the transformer is held fully or partially magnetized, the output of the secondary becomes limited.
Bill Beauregard wrote:
WerkSpace wrote:I collect old aircraft generators and they can be set up similar to the earlier engine driven welders.
http://www.api-assembled.com/design/tech/welder/welder.htm
Bill Beauregard wrote: As to how these machines change voltage I don't know. They have ranges of amperage, then fine control is done with voltage. At lower voltage arc length has more effect on voltage, therefore amperage. You are able to bury the electrode, melting lots of rod surrounded by cold steel preventing drips. As you used up substantial heat melting rod, less is dumped into the work piece. It freezes sooner.


I was referring to the Lincoln SA__ machines. I guess voltage is either controlled with the rheostat or engine throttle. Might amperage be a matter of varying inductance?
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Re: Voltage/current curves

Postby Bill Beauregard » Fri Jan 23, 2015 8:34 am

How then do they control amperage? With a MIG machine as voltage or electrical pressure rises more pressure pushes more current across the arc. I'm not sure I understand how it's done on a stick machine.
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Re: Voltage/current curves

Postby WerkSpace » Fri Jan 23, 2015 1:04 pm

Last edited by WerkSpace on Fri Jan 23, 2015 3:58 pm, edited 1 time in total.
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Re: Voltage/current curves

Postby p4nh4ndle » Fri Jan 23, 2015 3:18 pm

WerkSpace wrote:I collect old aircraft generators and they can be set up similar to the earlier engine driven welders.
http://www.api-assembled.com/design/tech/welder/welder.htm
Bill Beauregard wrote: As to how these machines change voltage I don't know. They have ranges of amperage, then fine control is done with voltage. At lower voltage arc length has more effect on voltage, therefore amperage. You are able to bury the electrode, melting lots of rod surrounded by cold steel preventing drips. As you used up substantial heat melting rod, less is dumped into the work piece. It freezes sooner.


That seems like a fun project if you have the parts on hand and some money/time to blow ;D

For the rest of us plebes, a used engine welder or an inverter is probably the way to go. Still, a good resource to demonstrate the function of those welders/parts.
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Re: Voltage/current curves

Postby Bill Beauregard » Fri Jan 23, 2015 7:13 pm



I have a number to choose from, in my obsession to weld as good as Field Res, (Travis Field) I'll buy what I have to. At present I have a Dynasty 280DX, A Bobcat 250, A Twentieth Century 295A AC with three voltage taps, an AC/DC Twentieth Century beater 295A transformer welder, and I think I gave away the best welder in the world a 194_ Westinghouse monster 600 A.
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Re: Voltage/current curves

Postby wheresmejumper » Sat Jan 24, 2015 12:23 pm

You dont need any more welders to be as good as good as travis
on a pipeline speed is king,then you need to adjust both amperage and voltage to get the sweet spot between you,the rod,and the machine.then you can put down metal both quick and clean.
To get good at pipe all you need is a half decent welder.
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