hesitation/surge coming from Dialarc HF-P

[dvice]

I have an older Miller welder at work and I was welding up a long aluminum tank yesterday.. I am working back and forth moving around to keep the whole thing from warping. So I was using the machine for 45 minutes and I noticed the machine surge...its hard to describe...almost like it lost UMPH for a second....its like a HUMMM and then back to formal.... almost like when you are about to lose power at work and the machines hmmm.

this happened several times...my auto darkening helmet even sensed the change . I was only doing .090" 5052 aluminum.. I has a 3/32 1.5% lanthanated electrode...I used a foot pedal....I have a water fed torch that's less than 1 year old( Radnor 20 F torch). anyone have an idea what it might be....is something going on the machine? we have a new miller Dynasty 350 but are waiting till our new room expansion is complete to put it into service... it is tight where we weld now...and the older machine is BIG.... I am going to buy the older machine from the company when we finally move it out.... so I want to know if it is dying!! thanks

Dvice

[Aeronca41]

Sounds like a bad connection somewhere. Besides checking in the machine also check plug/power wiring. Do you have another torch you can try?

[dvice]

I don't, the torch for the dynasty has different terminals than what the Dialarc uses, if I remember right.... could it have been a shifting of the ground clamp??

[Aeronca41]

Yes if it was loose. If it happens again I'd go for input power wiring first.

[duaneb55]

Being a "-P" version (Power Correction) I wonder if one or more of the input power correction capacitors has given up. They do have a finite life.

[Aeronca41]

I thought about that later. He can just disconnect them and see if it helps.

[dvice]

I just did some aluminum welding and it seemed to happen right when my puddle turned dirty!!..I wonder if it is bad gas...or a hestitation in the gas?.. I still have 700 psi in the bottle..... I had a super clean shiny puddle going....... then I heard the hesitation and spots showed up in my puddle..... I did not touch the electrode either......
dvice

[duaneb55]

I thought about that later. He can just disconnect them and see if it helps.

He could providing the power supply circuit and breaker are large enough to handle the increase in amperage draw while welding.

[tarry99]

He could providing the power supply circuit and breaker are large enough to handle the increase in amperage draw while welding.

So Expand on that statement a little............I'm Confused.....Are you saying with the PF missing or inoperable there would be an increase in Amperage now needed from the source? Is that based on if the welding was continuous...........as opposed to just a few minutes at a time?

Does this power issue not also fit a temporary brake down of the Contactor?

[Aeronca41]

Here is a link to an old thread on PF correction
http://www.millerwelds.com/resources...alled-proof-of


There are two kinds of power that can be measured and mathematically calculated-apparent power and real power. If the power factor is 1, they are equal, which is the best case. If the load is heavily inductive, such as high-current welding with a transformer-based machine, the current drawn from the line will tend to lag the voltage and reduce the power factor. In this case, apparent power becomes higher than real power, but only real power actually does work. A capacitive load causes the current to lead the voltage, causing a power factor less than one, but with the opposite "polarity". So, if you have a lagging power factor due to the transformer, and add the appropriate size PF correcting caps to the circuit that essentially cancel out the inductive lag, you can bring PF back to 1 and make the two types of power equal again. If PF caps are bad or missing, your apparent power draw from the line will increase while welding. PF correction only helps if you are constantly welding. When you stop the arc, the caps remain in the circuit, reducing the PF, and thus wasting power. PF correction is only recommended for industrial settings where if the machine is on, it's welding. If you leave the machine on when not welding, the apparent power at "idle" will be much higher than a unit without PF correction (but not as high as if you were welding). This is due to the fact that the capacitors now act as an "AC resistance" ( called impedance) connected across the line, based on their capacitive reactance and (very, very small) installed series resistance. It would be just like putting a big resistor across the incoming power line that generates heat to warm up the shop. Costs money to run but doesn't do any welding.

There is a lot more to this whole power factor thing; just google it if you're interested....or perhaps I've already bored you to tears on the topic. :-)

So, what duaneb55 was saying is that if your breaker happens to be marginally sized for your welder with PF correction, it is possible the increase in apparent power caused by removed or failed PF caps might trip the breaker while welding at higher currents. This is in my estimation (one guy's opinion) a rather low risk especially if you are only welding a few minutes at a time, but his statement is quite valid.

So, what he and I were both thinking was that if your PF caps are going bad, they might cause the glitching you describe. Not a sure thing, but possible.

I dont understand your second question about break down of the contactor-can you elaborate?

[tarry99]

Here is a link to an old thread on PF correction
http://www.millerwelds.com/resources...alled-proof-of

I dont understand your second question about break down of the contactor-can you elaborate?

Aero: What I meant is similar to the problem I had with my Dialarc when my machine would intermediately weld the problem was traced to the points within the Contactor that were either overheated , burnt, blackened , or damaged that apparently would not allow full power to flow through them.............Just thought that may also play a part in what this fellow had for a problem........whereby after welding for a long period the machine seemed to loose power???

[tarry99]

Aero: One more question.........relating to your PF response above..

"So, what duaneb55 was saying is that if your breaker happens to be marginally sized for your welder with PF correction, it is possible the increase in apparent power caused by removed or failed PF caps might trip the breaker while welding at higher currents. This is in my estimation (one guy's opinion) a rather low risk especially if you are only welding a few minutes at a time, but his statement is quite valid."

My normal routine with my PF equipped Dialarc HF would be to shut if off as soon as welding was completed........and that might be 3 minutes but hardly never more than 15 minutes at a time.........and that might be a few times daily and only a few times per week...........the point is I'm not under the hood for long periods and the reason I'm quick to shut it off is partly due that the Bernard Cooler is pretty noisy and it's just me in the shop..........

So my question is based on my use factor and the fact that the machine is not in use or turned on for long periods of time and my breaker to the welder is only 50 amps and never had problem although I have a 100 coming into the panel.............would in this instance be just as beneficial to leave the PF caps connected? I mean I never gave the power cost a real debate..............I really was more **** about loosing whatever Argon was left in the line between uses?

What say you?

[Aeronca41]

Personal opinion-would love to hear what others think-is that the way you're using it, it just doesn't make a lot of difference either way.

[duaneb55]

Aeronca41, Thanks for jumping in with an excellent explanation.

tarry99, A review of the input power requirements at rated output show [email protected] for the standard unit and only [email protected] for the PFC version.

Not sure why the Owner's Manual doesn't list it but idle amp draw for the standard unit on 230V is 6A while the PFC version is [email protected] due to keeping the capacitors charged.

I know of at least one "-P" owner that wired up a power relay to power the input capacitors when the main contactor was energized. This way the machine would idle at the lower 6A but still take advantage of the PFC when the relay closed to power the capacitors. I have no idea how well this set up worked but I would imagine if it didn't work well he would eliminate the by-pass.

[Aeronca41]

Aero: What I meant is similar to the problem I had with my Dialarc when my machine would intermediately weld the problem was traced to the points within the Contactor that were either overheated , burnt, blackened , or damaged that apparently would not allow full power to flow through them.............Just thought that may also play a part in what this fellow had for a problem........whereby after welding for a long period the machine seemed to loose power???

Ok-thanks for the explanation-understand now. Yes, you are correct that might be the problem. Certainly worth a look at the contacts.