Plasma Cutter

[K8MHZ]

i disagree.

the atoms get hot from resistance of movement, which generates self-heat, then melts.
you are adding energy from the burning of gas, the burning gas does not actually melt the metal :thumbsup:

Never mind. Plasma restrictions and all.

 

[iwire]

My opinion.

Not a welder.

630 does not apply

My opinion is you have overlooked the scope of 630.

2014 NEC

I. General
ARTICLE 630
Electric Welders
630.1 Scope. This article covers apparatus for electric arc
welding, resistance welding, plasma cutting, and other
similar welding and cutting process equipment that is connected
to an electrical supply system.

 

[K8MHZ]

My opinion is you have overlooked the scope of 630.

2014 NEC

Not at all. That's the part that is screwy. The scope does say plasma cutting, no doubt about it.

Of the four parts of 630, which apply to plasma cutters?

Edit to add: Which apply to EDM machines, which are also electrical cutting apparatus?

 

[FionaZuppa]

Not at all. That's the part that is screwy. The scope does say plasma cutting, no doubt about it.

Of the four parts of 630, which apply to plasma cutters?

Edit to add: Which apply to EDM machines, which are also electrical cutting apparatus?

this same issue is also in 680. in 680 there are back references, but the back references do not specifically address the item in the section that used the back reference.

for 630, use whatever you see applicable from your professional viewpoint.

my forum sig should be "nec needs some fixin"

 

[K8MHZ]

this same issue is also in 680. in 680 there are back references, but the back references do not specifically address the item in the section that used the back reference.

my forum sig should be "nec needs some fixin"

If the NEC meant that plasma cutters should be regulated the same as arc welders, how difficult would it have been to say 'Arc Welders and Plasma Cutters'?

Plasma cutters don't use arcs to do their job. They use an accelerated jet of plasma, the fourth state of matter, to burn through metal.

 

[steve66]

If the NEC meant that plasma cutters should be regulated the same as arc welders, how difficult would it have been to say 'Arc Welders and Plasma Cutters'?

I agree. The scope of 630 may say plasma cutters, but I can't find a single paragraph that I believe would apply to a plasma cutter.

Each part of 630 seems to apply to only welders - ie. Arc Welders, Resistance Welders, and Welding Cable. With "Welding" in the title, I believe that excludes it from applying to a plasma cutter.

Maybe they put "plasma cutter" in the scope thinking some day they may add some paragraph that applies to plasma cutters?

 

[K8MHZ]

Maybe they put "plasma cutter" in the scope thinking some day they may add some paragraph that applies to plasma cutters?

Knowing which code cycle it was first added in may give a clue.

 

[FionaZuppa]

Plasma cutters don't use arcs to do their job. They use an accelerated jet of plasma, the fourth state of matter, to burn through metal.

how exactly is that plasma created ?? i suspect an arc :thumbsup:

 

[iwire]

Not at all. That's the part that is screwy. The scope does say plasma cutting, no doubt about it.

So you claim an article that has a scope that includes plasma cutters does not apply to plasma cutters and a an article in chapter 6 that has a scope that does not include plasma cutter applies to plasma cutters.

Cerratily if 630 did not exsit perhaps 670 would be the place to go.

My opinion.

Not a welder.

630 does not apply

670 does apply

670 requires max. current to be on nameplate, so I would go with 125% of 61 amps.

You are free to your opinion but at this point I am stepping out as to me you are so far in left feild any discussion is fruitless.

Of the four parts of 630, which apply to plasma cutters?

According to the scope ... all of it.

 

[iwire]

I agree. The scope of 630 may say plasma cutters, but I can't find a single paragraph that I believe would apply to a plasma cutter.

The only place the word 'plasma' shows up in the NEC is in the scope of 630.

I would wire it as a resistance welder without even a second thought.

You guys can wire yours as you wish.

 

[K8MHZ]

The only place the word 'plasma' shows up in the NEC is in the scope of 630.

I would wire it as a resistance welder without even a second thought.

You guys can wire yours as you wish.

Why, when a plasma cutter has more in common with an arc welder than with a resistance welder.

Take note of the duty cycle ratings. Arc welders have a table that goes to 100%. Resistance welders, only 50%. The OP's cutter has a rating of 100%. Perhaps you should have had that second thought. You can wire it like a table saw if you like, but the code section about resistance welders has nothing to do with plasma cutters.

 

[iwire]

Why, when a plasma cutter has more in common with an arc welder than with a resistance welder.

Take note of the duty cycle ratings. Arc welders have a table that goes to 100%. Resistance welders, only 50%. The OP's cutter has a rating of 100%. Perhaps you should have had that second thought. You can wire it like a table saw if you like, but the code section about resistance welders has nothing to do with plasma cutters.

You are right, I was thinking arc and typed resistance.


But in reality it does not matter what I typed, when I have wired welders I have used full size circuits without bothering with duty cycles. Just like most HVAC and motor loads I wire do not take advantage of the rules allowing a larger OCPD than the conductor ampacity suggests.


If I was the OP I would ignore the duty cycle, install a full sized circuit and collect the money.

 

[K8MHZ]

So you claim an article that has a scope that includes plasma cutters does not apply to plasma cutters and a an article in chapter 6 that has a scope that does not include plasma cutter applies to plasma cutters.

That is the way it is written. It may not be what you want to read, or want to apply, but that is the way it is written.

Cerratily if 630 did not exsit perhaps 670 would be the place to go.

Or, if 630 does not provide the needed information

You are free to your opinion but at this point I am stepping out as to me you are so far in left feild any discussion is fruitless.

Why am I 'in left field'? Just because I don't agree with you?

According to the scope ... all of it.

How can both Part I and Part II apply to the same device? It's one or the other, or neither.

 

[K8MHZ]

You are right, I was thinking arc and typed resistance.


But in reality it does not matter what I typed, when I have wired welders I have used full size circuits without bothering with duty cycles. Just like most HVAC and motor loads I wire do not take advantage of the rules allowing a larger OCPD than the conductor ampacity suggests.


If I was the OP I would ignore the duty cycle, install a full sized circuit and collect the money.

So, you would use the Eff rating of 55 amps? Would you use or ignore 125%?

What about spot welders? Using full size circuits for them is definitely a waste of money. That's just for thought and possibly a different thread, no need to answer.

 

[K8MHZ]

how exactly is that plasma created ?? i suspect an arc :thumbsup:

Kind of... The arc is the 'electrical' part of the discharge. The plasma is the superheated substance that behaves like a gas and can be pressurized and blown through an orifice to cut metal in the manner an oxyacetylene cutting torch works, only better.

Plasma can be made several ways. Any kind of heating will turn gas into plasma at standard pressure if enough heat is put to it. Actually, using an arc to create plasma is known as creating an 'artificial plasma'.

Low pressures can also create plasma. Our ionosphere is a sphere of plasma. Radio operators love the ionosphere because we can use it to refract signals and land them anywhere on the planet.

So yes, you can use an arc to create plasma, but plasma is a state of matter, not an arc.

 

[Mgraw]

This is from the CUTMASTER 152 manual.

 

[Mgraw]

I am grappling with a plasma cutter. Is this thing a welder? Does Art. 630 apply? Art. 670?

Supposing I were of a mind to put this thing on a 208V 3-Phase circuit. What on that nameplate do I pay attention to...? :blink:

View attachment 15507

I would say it is a welder. Plasma cutters are manufactured to standards that are included in "arc welding equipment standards"

 

[kwired]

Kind of... The arc is the 'electrical' part of the discharge. The plasma is the superheated substance that behaves like a gas and can be pressurized and blown through an orifice to cut metal in the manner an oxyacetylene cutting torch works, only better.

Plasma can be made several ways. Any kind of heating will turn gas into plasma at standard pressure if enough heat is put to it. Actually, using an arc to create plasma is known as creating an 'artificial plasma'.

Low pressures can also create plasma. Our ionosphere is a sphere of plasma. Radio operators love the ionosphere because we can use it to refract signals and land them anywhere on the planet.

So yes, you can use an arc to create plasma, but plasma is a state of matter, not an arc.

So isn't the load seen by the supply circuit going to be related to the operation/conditions of that arc regardless of what is produced for plasma? Wouldn't this have most of the same characteristics that an arc welder has? Major factors that would apply to necessary circuit ampacity and overcurrent protection would be related to the duty cycle just like for an arc welder wouldn't they. So whether or not you had an arc welder or a plasma cutter, if the power rating and duty cycle is same for both then you should have same general supply circuit requirements shouldn't you?

It may be more common to see higher duty cycle for the plasma cutter but what I am saying is if the welder had the same duty cycle then the circuit requirements would be same for both.

 

[Fulthrotl]

So isn't the load seen by the supply circuit going to be related to the operation/conditions of that arc regardless of what is produced for plasma? Wouldn't this have most of the same characteristics that an arc welder has? Major factors that would apply to necessary circuit ampacity and overcurrent protection would be related to the duty cycle just like for an arc welder wouldn't they. So whether or not you had an arc welder or a plasma cutter, if the power rating and duty cycle is same for both then you should have same general supply circuit requirements shouldn't you?

It may be more common to see higher duty cycle for the plasma cutter but what I am saying is if the welder had the same duty cycle then the circuit requirements would be same for both.

plasma cutters, at least the smaller portable ones, often run on 120 or 240, and draw the same current
flow for the same thickness of material. the demand cycle sometimes varies with the voltage, sometimes
does not..

if i saw maximum current on the machine was 48 amps, i'd put it on a 60 amp branch circuit.
anyone who's ever used one understands the PITA factor of having it turn off in the middle of
a cut.

 

[iwire]

That is the way it is written. It may not be what you want to read, or want to apply, but that is the way it is written.

Dude, you have it backward, the scope of 630 tells us in black and white it applies. You are claiming it does not. That means you are the one having trouble understanding how it is written.

Why am I 'in left field'? Just because I don't agree with you?

No, not at all.

I say you are in left field because you agree that the scope of article 630 says it applies to plasma cutters at the same time you are telling us it does not.

How can both Part I and Part II apply to the same device? It's one or the other, or neither.

I don't know but I do know that the article applies to plasma cutters, you can't say it does not.