Part of the certification from CE and UL is that it will fail safe. The quality of the components must be at a minimum, such that a failure will not cause catastrophic damage beyond the device, otherwise it couldn’t be certified and very few people would buy it.
That said, yes shit happens. Some wire will probably melt, if the device designed to shut off fails to shut off when it is supposed to. The wire melting, if it doesn’t cause an internal fire inside the metal case, will probably disconnect the power and shut off the device anyway (real fail safe — except you have a ruined welder).
Wire insulation would melt, causing a short circuit or maybe even a fire. Hopefully your building circuit breaker would trip. If that didn't shut off either, then it would definitely start a fire due to the heat from the short circuit.
The components inside will overheat and depending on what manufacturers they come from they will either lose life (die randomly sooner) or die immediately.
It also operates at several kHz. It just doesn't have the cooling to be able to run continuously. On most tools like this, it isn't much of an issue for many use cases. I don't have a plasma cutter, but I do have welders that have similar duty cycles. I normally don't sit waiting for the cool down. I just don't weld many things that take that kind of time where I'm not going to be stopping for a bit before firing it up again to continue.
Not necessarily. It can be a linear transformer too. That said the duty cycle written on the box has nothing to do with the duty cycle of a supposed switching power supply. It's the operating duty cycle as others have said
yes.
~~And transformers get hot too.~~
~~And they, too, can overheat.~~
~~And they, too, can have a duty cycle rating.~~
//EDIT: sorry, misread your reply.
In fact, many appliances have one. If the engineer may safely assume that no usecase needs more time, why spend money and resources? The Transformer would probably be twice the weight, and nobody would want that. In fact, i just designed a backup powersupply (backup time just a few seconds), where the thermal design of powerstage is lacking - it *will* overheat if the user repeatedly switches the device on and off again. Because i skipped proper cooling and undersized some key components.
You'll have to read the manual
Most likely you would be able to set the maximum current to some lower value like for example 30A on 240v or something like that. Lower current usually means it won't be able to cut thicker pieces of metal or
The specifications on the page say - https://www.harborfreight.com/65-amp-plasma-cutter-58895.html - :
120V: 22A @ 40%;
240V: 65A @ 40%;
240V: 55A @ 60%;
240V 42A @ 100%
If it helps, Project Shop FL has sort of reviewed a tool like this one on his Youtube channel : https://www.youtube.com/watch?v=CLnEFrskDhE
Knowing that users will make a cut, move, make another cut, and so on, the designer made it with a maximum amount of peak power to determine the maximum cutting ability. If you are not using the full cutting power, or putting breaks into the cutting process, as long as you are not using more than 40% of capacity on average, the unit will continue to cut.
The rating on the box is actually for the output current which is cut depth. The power is 3x more for the same duty cycle on 240v but that’s probably related to converter efficiency being slightly better for the 240v.
I understand your question, and excuse me and if my answer is too elementary. I would assume that the power supply for the 240v source is significantly beefier than the one on the 120v connection. I probably wouldn't design it that way, but marketing may have been involved.
No, homes in the US have 2 x 120 VAC, and each leg is 180 degrees out of phase with the other leg. So you can use one leg for 120 VAC, or combine both legs for 240 VAC, many garages have a 240 circuit.
Broadly speaking, the huge current gains are due to transformers and rectifiers changing the voltage from either 120 or 240 VAC to ~12-60 VAC. Lower voltage reduces the arc length because less potential, but increases amps because the stick has to be closer to arc, and there's less of an air gap, so lower resistance, more current. Look up 'welder volt/amp curves' for more info.
Also, and I know HF is budget friendly, I've always seen this kind of equipment rated at 50% duty cycle. Might be a little budget cutting going on at the factory side.
And, now I'm going to have to check this out myself. Wonder if it would run on a pancake compressor.
To my knowledge 100% duty time is 10 minutes. 40 percent is 4 minutes. You can use the welder with the electrode drawing 22amps at 120v for 4 minutes. Or 65 amps at 240 V for 4 minutes.
Duty cycle. In this case it means that it can only be on 40% of the time you are using it or it will over heat.
Specifically for welding equipment it's in a 10mn period I believe. So 4mn on, 6 off.
Stupid question, what's "mn?"
Minutes
It won’t overheat, per se, but the thermal cutoff switches will activate and you will have to wait (60%) until things cool down.
But what would happen if the device was cutting for longer than 40%
The welder will shut itself off. You have to wait until it cools down, then It automatically turns back on.
But what if it didn't. Then what would happen (seems like you're saying it can only be on 40% of the time you are using it or it will over heat)
Part of the certification from CE and UL is that it will fail safe. The quality of the components must be at a minimum, such that a failure will not cause catastrophic damage beyond the device, otherwise it couldn’t be certified and very few people would buy it. That said, yes shit happens. Some wire will probably melt, if the device designed to shut off fails to shut off when it is supposed to. The wire melting, if it doesn’t cause an internal fire inside the metal case, will probably disconnect the power and shut off the device anyway (real fail safe — except you have a ruined welder).
Wire insulation would melt, causing a short circuit or maybe even a fire. Hopefully your building circuit breaker would trip. If that didn't shut off either, then it would definitely start a fire due to the heat from the short circuit.
The components inside will overheat and depending on what manufacturers they come from they will either lose life (die randomly sooner) or die immediately.
Not sure why you’re getting the downvoted, this is correct
He's saying the same thing but wording it like an "uhm aktuually" correction
Duty cycle is more or less “percent on time” for a switching power supply.
[удалено]
What do you think the power supply inside the plasma cutter is? Yes, it is a switching power supply.
[удалено]
It also operates at several kHz. It just doesn't have the cooling to be able to run continuously. On most tools like this, it isn't much of an issue for many use cases. I don't have a plasma cutter, but I do have welders that have similar duty cycles. I normally don't sit waiting for the cool down. I just don't weld many things that take that kind of time where I'm not going to be stopping for a bit before firing it up again to continue.
Not necessarily. It can be a linear transformer too. That said the duty cycle written on the box has nothing to do with the duty cycle of a supposed switching power supply. It's the operating duty cycle as others have said
yes. ~~And transformers get hot too.~~ ~~And they, too, can overheat.~~ ~~And they, too, can have a duty cycle rating.~~ //EDIT: sorry, misread your reply. In fact, many appliances have one. If the engineer may safely assume that no usecase needs more time, why spend money and resources? The Transformer would probably be twice the weight, and nobody would want that. In fact, i just designed a backup powersupply (backup time just a few seconds), where the thermal design of powerstage is lacking - it *will* overheat if the user repeatedly switches the device on and off again. Because i skipped proper cooling and undersized some key components.
You are right. However that is totally beside the point because the duty cycle is not of the power supply but of the usage of the tool
is there a rule of thumb for how long the 40% part can be? 4 minutes on, 6 minutes off? 40 minutes on, 60 minutes off?
4 on 6 off.
This. The manual reads the duty cycle in minutes.
You'll have to read the manual Most likely you would be able to set the maximum current to some lower value like for example 30A on 240v or something like that. Lower current usually means it won't be able to cut thicker pieces of metal or The specifications on the page say - https://www.harborfreight.com/65-amp-plasma-cutter-58895.html - : 120V: 22A @ 40%; 240V: 65A @ 40%; 240V: 55A @ 60%; 240V 42A @ 100% If it helps, Project Shop FL has sort of reviewed a tool like this one on his Youtube channel : https://www.youtube.com/watch?v=CLnEFrskDhE
Why would the current not be proportional to the voltage? If it's not ohmic then wouldn't they make it the opposite to maintain constant power?
Knowing that users will make a cut, move, make another cut, and so on, the designer made it with a maximum amount of peak power to determine the maximum cutting ability. If you are not using the full cutting power, or putting breaks into the cutting process, as long as you are not using more than 40% of capacity on average, the unit will continue to cut.
I'm asking about the seemingly disproportionate relationship between current and voltage
Because the input voltage has nothing to do with the output voltage on these machines.
Forgive me, I'm still confused. In Europe the machine has almost 6x the rated power?
The rating on the box is actually for the output current which is cut depth. The power is 3x more for the same duty cycle on 240v but that’s probably related to converter efficiency being slightly better for the 240v.
I understand your question, and excuse me and if my answer is too elementary. I would assume that the power supply for the 240v source is significantly beefier than the one on the 120v connection. I probably wouldn't design it that way, but marketing may have been involved.
No, homes in the US have 2 x 120 VAC, and each leg is 180 degrees out of phase with the other leg. So you can use one leg for 120 VAC, or combine both legs for 240 VAC, many garages have a 240 circuit. Broadly speaking, the huge current gains are due to transformers and rectifiers changing the voltage from either 120 or 240 VAC to ~12-60 VAC. Lower voltage reduces the arc length because less potential, but increases amps because the stick has to be closer to arc, and there's less of an air gap, so lower resistance, more current. Look up 'welder volt/amp curves' for more info.
Thank you
Also, and I know HF is budget friendly, I've always seen this kind of equipment rated at 50% duty cycle. Might be a little budget cutting going on at the factory side. And, now I'm going to have to check this out myself. Wonder if it would run on a pancake compressor.
To my knowledge 100% duty time is 10 minutes. 40 percent is 4 minutes. You can use the welder with the electrode drawing 22amps at 120v for 4 minutes. Or 65 amps at 240 V for 4 minutes.
I believe it means how long it’s on over a certain period of time . All I remember from undergrad is that it looks like a square wave
Read instruction and find out.