Running a 3 Phase KEMPPI PS2800 Welder on Single Phase

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Steggy
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Re: Running a 3 Phase KEMPPI PS2800 Welder on Single Phase

Post by Steggy »

SteveM wrote: Thu Jan 27, 2022 4:03 pm OK, for the uninformed, please explain how something like a welder can be 3-phase.

I can see in motors where the different phases kick in to provide rotation, but 3-phase welder sounds like a 3-phase light bulb to me.

Steve

Three-phase welders are very common in industry and produce an arc quality that cannot be readily achieved from single-phase power using only a transformer and rectification.

Meanwhile, I'll give you something to ponder. The alternator in your automobile is a three-phase device producing the direct current necessary to support the electrical loads and charge the battery. :D
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John Hasler
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Re: Running a 3 Phase KEMPPI PS2800 Welder on Single Phase

Post by John Hasler »

BigDumbDinosaur writes:
If the power source is two-phase, connecting the inputs of a dual-channel ’scope to the
hot legs would reveal two sine waves exactly 180 degrees out of phase.

90 degrees. 180 degrees is just opposite ends of center-tapped single phase.

Please don't call the grounded conductor of a three-phase system the neutral unless it really is the neutral (that is, the center of the wye).
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Re: Running a 3 Phase KEMPPI PS2800 Welder on Single Phase

Post by John Hasler »

BigDumbDinosaur wrote: Thu Jan 27, 2022 2:26 pm
John Hasler wrote: Thu Jan 27, 2022 10:38 amBTW do *not* try to run any three-phase equipment other than a motor from a "static converter". It would be more accurate to describe a static converter as converting a three-phase motor to run on single phase than to describe it as converting single-phase to three-phase.

It depends on the converter. The higher-end ones produce a good-quality output, with approximately equal voltages on all legs. They could be used for non-motor loads, although I would draw the line at powering an arc welder with one.

On the other hand, the “low cost” converters are barely suitable for running a motor. I'd use one to run a three-phase light bulb, though. :lol:
By "static converter" I refer to the devices that contain only phase shifting capacitors and a relay. If you look at the "output" of one of those with a scope with no motor connected you won't see anything resembling three-phase.
Last edited by John Hasler on Fri Jan 28, 2022 8:57 am, edited 1 time in total.
John Hasler
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Re: Running a 3 Phase KEMPPI PS2800 Welder on Single Phase

Post by John Hasler »

SteveM wrote: Thu Jan 27, 2022 4:03 pm OK, for the uninformed, please explain how something like a welder can be 3-phase.

I can see in motors where the different phases kick in to provide rotation, but 3-phase welder sounds like a 3-phase light bulb to me.

Steve
The output of a three-phase full wave bridge rectifier has fairly low ripple and never goes to zero even without any filtering. Draw a full-wave rectified sine wave. Draw another over it shifted over 120 degrees. Draw a third, shifted another 120 degrees.
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Re: Running a 3 Phase KEMPPI PS2800 Welder on Single Phase

Post by NP317 »

Area under the curve of the graph. The more phases the higher the energy delivered.
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