240V Welder safe to run with 208V 3 phase system?

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PE (always learning)

PE (always learning)

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I have a project I'm working on where I am providing electrical design for a stand alone shop class. The school is buying five Thunderbolt 210 stick welders and the cut sheets show that the equipment has an input power of 240V, single phase. My electrical service entrance for this stand alone shop class is 120/208V, 3 phase, 4 wire. Can I run this equipment with 208V single phase power? I don't see anything on the cut sheets showing a duel voltage rating or an input for 208V for this equipment. Cut sheets attached for reference..
 

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I know my millermatic 210 and some others will do fine on 208, and I suspect this one will as well since it’s 120/240 rated.
mine is 120 volt, or simply change a plugon the end of the cord for 240. Just adjust the output amperage to suit you. The numbers on the dial won’t exactly match but I don’t really go by them anyway. I go by sound

edit- saw the 160 has two plugs like my old 210.
Mine pulls too much on 120 when it’s burning hot.

I suspect that’s why they don’t offer the 120 plug for the 210
 
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engineerintraining12 said:
I have a project I'm working on where I am providing electrical design for a stand alone shop class. The school is buying five Thunderbolt 210 stick welders and the cut sheets show that the equipment has an input power of 240V, single phase. My electrical service entrance for this stand alone shop class is 120/208V, 3 phase, 4 wire. Can I run this equipment with 208V single phase power? I don't see anything on the cut sheets showing a duel voltage rating or an input for 208V for this equipment. Cut sheets attached for reference..
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I'd be inclined to just buy a smallish 3 phase 208 to 240 transformer. A 75 kva xfmr would likely be adequate. Would probably not cost more than $2000.
 
engineerintraining12 said:
I have a project I'm working on where I am providing electrical design for a stand alone shop class. The school is buying five Thunderbolt 210 stick welders and the cut sheets show that the equipment has an input power of 240V, single phase. My electrical service entrance for this stand alone shop class is 120/208V, 3 phase, 4 wire. Can I run this equipment with 208V single phase power? I don't see anything on the cut sheets showing a duel voltage rating or an input for 208V for this equipment. Cut sheets attached for reference..
Click to expand...

ask the same question here;

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engineerintraining12:

I can not answer your question because I am not where the equipment and manual are:

However, some basics.

What are the electrical characteristics of an arc discharge? In some regions of current it looks like a negative incremental resistance. This means you can not directly drive an arc from a voltage source. Rather your source to the arc needs to be a current source, or at least current limited which then in that region is a current source.

In inexpensive AC sourced welders this is usually accomplished by use of series inductance.

A lower source voltage would just limit the maximum current. Therefore, 208 vs 240 would probably be of no problem unless you needed the maximum current from the welder.

What might be a problem relates to voltage of your circuitry relative to earth grounding for both equipment and personnel. If effectively there is isolation via a transformer between input AC and output AC or DC, then a floating 208 input may be OK.

.
 
Open Neutral said:
Is there a similar 3-ph welder the school can buy instead?
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I called Miller and they said that a similar welder that operates at 208V would cost about twice as much as the Miller Thunderbolt 210. I asked if the Thunderbolt 210 could operate at 208V and they said the equipment had a 20% tolerance in voltage and can operate at 208V, but the output won't be quite as good. I think that the reduced output is not as much of a concern as this is a school and not a production facility.
 
engineerintraining12 said:
I called Miller and they said that a similar welder that operates at 208V would cost about twice as much as the Miller Thunderbolt 210. I asked if the Thunderbolt 210 could operate at 208V and they said the equipment had a 20% tolerance in voltage and can operate at 208V, but the output won't be quite as good. I think that the reduced output is not as much of a concern as this is a school and not a production facility.
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I agree with your findings. Chances are your voltage at the school is 212-215V anyway.
students wont realize it has to be turned up higher to weld the 3/16(?) metal you teach with..

On my Miller the cooling fan is 120, so I need the neutral when I weld on 240VAC.
I suspect if you look at the 160 specs and the amp charts you will see why the 210 isn’t offered anymore with the interchangeable 120V plug like mine.
 
I would also caution that I had this same discussion awhile back and was told by a manufacturer that a similar 120/240 single phase welder had some automatic voltage-sensing equipment onboard that would cause the machine to not work if input voltage dropped below 208v. Essentially the machine would try to recalibrate for 120 or 240 input and in the middle was gray and the machine would not operate. So the caveat was if the 208 service is riding high you might be OK, but might not be...
 
wolfsburged said:
I would also caution that I had this same discussion awhile back and was told by a manufacturer that a similar 120/240 single phase welder had some automatic voltage-sensing equipment onboard that would cause the machine to not work if input voltage dropped below 208v. Essentially the machine would try to recalibrate for 120 or 240 input and in the middle was gray and the machine would not operate. So the caveat was if the 208 service is riding high you might be OK, but might not be...
Click to expand...
The sensing circuity makes total sense ... there are only 2 powered input leads and the ECG, but the "amps knob" goes from 20-80 and 20-160 only depending on the input voltage... no selection switch.

I think if I were the designer, I would have allowed high to be between 190-250 and noted that output should be limited to 140 amps for nominal 208 systems. The thermal overload should take care of those who ignore it.
 
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