PA140st arc stability

[DaveO]

It's a overcurrent light as well.

Does that suggest a supply problem? The mains issue was discussed earlier and ruled out, I thought, but machine number 3...?

[performance]

It could be an internal resistor value issue. I am not familiar with the revised 140st's internally, but on some of the older ones, there was an adjustment that could be made.

[NWD43]

Does that suggest a supply problem? The mains issue was discussed earlier and ruled out, I thought, but machine number 3...?

It's absolutely not a mains issue, I can run anything I want to on this circuit without fail. Measures 139VAC under load. I have tried it on 120V and it displays the same performance except for the limitation on high end current. It DOES work better than the other two before it so I'm happy for that.

PERFORMANCE: What is an "over current" lamp? If I set the current to 10A shouldn't the machine supply 10A into the load? How can it supply more than it's set for and then complain that I'm asking for too much current?? I should think that, normally, we get less current than we expect due to I/R losses in the leads, resistance between clamp and work, etc., but never more current than we call for. What part of this do I not understand?

As I said before, I'm prepared to keep and use this thing for all the things it can do, and keep my expectations under control.

Neil

[performance]

First, it is an analog machine. Every unit has a margin of error in settings overall...Resistors and such have a 10% margin of error...so at times things can go a little over or under. The display is there for general reference and cannot be expected to be spot on. Equivalent models in most name brands do not even offer this feature at all. The overcurrent/overheat light is multi color. It can sense an over current or duty cycle issue, and changes color to reflect that (not sure which color is assigned to which on the newer units. That would be a Ray question).

I have no answer why the overcurrent/voltage or duty cycle light is coming on other than the resistor value is slightly off in the circuit that senses it or the arc initiation...I am not the electronics expert...but I do know some general things about the welders operation and design.

I will say this....that 139 volts under load is too high of voltage for what the machine is rated for 120V +- 10%. This could be causing the issue with the over voltage light flashing on. Is this being supplied by a generator?

[joshuab]

It's absolutely not a mains issue, I can run anything I want to on this circuit without fail. Measures 139VAC under load.

Holy cow! That's not normal. See below, from ANSI C84.1.



You are at least 10 volts over the upper end of the normal range for 120v mains power.

EDIT: Dang it. The forum resized my image so it's not readable. Here's the original link.

http://www.pge.com/includes/docs/pdf..._tolerance.pdf

To sum up, a nominal upper limit for 120v power is around 127 volts. I don't know what you have been running on that circuit "without fail," but you're lucky to not have destroyed it with over-voltage.

[NWD43]

Holy cow! That's not normal. See below, from ANSI C84.1.



You are at least 10 volts over the upper end of the normal range for 120v mains power.

EDIT: Dang it. The forum resized my image so it's not readable. Here's the original link.

http://www.pge.com/includes/docs/pdf..._tolerance.pdf

To sum up, a nominal upper limit for 120v power is around 127 volts. I don't know what you have been running on that circuit "without fail," but you're lucky to not have destroyed it with over-voltage.

Of course you're right!! My error, I meant to say 239VAC for the circuit. The 120V circuit is nominally 120V.

Neil