Looking for some help understanding OCV's

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The way I understand it, OCV is what allows you strike an arc when stick welding. But what happens after you strike an arc and start welding? Does the voltage drop down? Does the voltage have any effect on the arc itself? I ask because watching one of our machines at work today, I noticed that the voltage on the display stayed around the mid 70's range (miller pipe pro 304). Guy was running 5/32 6010 5p at around 80 amps. Would like to better understand OCV's and it's effect while welding.Operating Engineers Local 3Lincoln SA 200Victor TorchDewalt Grinder10 lbs SledgeWhat more do ya need!


Reply:Here's a good background Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:From the Lincoln Handbook of Welding and Design:


Lincoln SA200 manual:

"USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:OCV or Open Circuit Voltage is what the volts are before you strike an arc. If using CC (constant current) then voltage will drop when welding. If using CV (constant voltage) then volts wont drop much if any but current will fluctuate. You said its a MILLER and I guess it has a CC and CV mode. Was it in CV when welding with 6010. BTW, hows the new job? Im sure as beautiful as it is driving thru the Sierras, it gets old.
Reply:

Originally Posted by MinnesotaDave

Here's a good background
Reply:Willie, your uphill question is explained on the right hand page of oldendumb's first picture.The low OCV vs high OCV affects the shape of the volt/amp curve. This change affects the arc characteristics when you pull a long arc momentarily during a whip and pause.In the volt/amp pics you can see one changes the amps more than the other as the arc length (voltage) changes.For your first question on watts, he isn't referring to watts, he is referring to the overlapping amperage ranges on the engine drive. Selecting a higher gear (coarse range setting) and reducing the fine dial can get you the same amps as a lower gear with the fine setting increased.Both of your questions are actually related to each other.The overlapping amp ranges are also described in the last pic he uploaded.Last edited by MinnesotaDave; 03-10-2018 at 06:07 PM.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:I was an annoying kid, "Why Daddy, Why? Now, I'm an annoying old man, "WHY?" If amps remain the same, and voltage increases, we get more heat. Longer arc length gives more resistance. In a series circuit, any point of resistance gets a bigger share of voltage. I've never been clear if a long arc, meaning more voltage means less amperage. Either way, more volts, longer arc will compound into much more voltage. Thinking out loud, I don't pretend it is fact; Does the short arc used with lower voltage also push a bigger share of the heat into the weld joint for more penetration? If burn off of electrode rate increases, deposit rate must increase. In the sense that dabbing filler, converting solid to liquid consumes BTUs, does this chill the weld metal already deposited?I envy those of you with SA-200 and similar machines. You control voltage with governor speed. Can this be controlled on a Miller Bobcat 250? I suspect higher range, with little fine amperage does this. I have no crisp, or soft control like Fieldres shows on his modern Lincoln.WillieAn optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:

Originally Posted by Willie B

I was an annoying kid, "Why Daddy, Why? Now, I'm an annoying old man, "WHY?" If amps remain the same, and voltage increases, we get more heat. Longer arc length gives more resistance. In a series circuit, any point of resistance gets a bigger share of voltage. I've never been clear if a long arc, meaning more voltage means less amperage. Either way, more volts, longer arc will compound into much more voltage. Thinking out loud, I don't pretend it is fact; Does the short arc used with lower voltage also push a bigger share of the heat into the weld joint for more penetration? If burn off of electrode rate increases, deposit rate must increase. In the sense that dabbing filler, converting solid to liquid consumes BTUs, does this chill the weld metal already deposited?I envy those of you with SA-200 and similar machines. You control voltage with governor speed. Can this be controlled on a Miller Bobcat 250? I suspect higher range, with little fine amperage does this. I have no crisp, or soft control like Fieldres shows on his modern Lincoln.Willie
Reply:

Originally Posted by Willie B

...I envy those of you with SA-200 and similar machines. You control voltage with governor speed. Can this be controlled on a Miller Bobcat 250? I suspect higher range, with little fine amperage does this. I have no crisp, or soft control like Fieldres shows on his modern Lincoln.Willie
Reply:Also think of it like a car battery.  A small one and big one will both sit at ~13 volts, but when you start a car, the small one has it's voltage sucked down a lot further while starting, and a big one will maintain voltage easier, but they both do gets sucked down.  Not uncommon for a battery to be pulled down to 10 volts while cranking.A transformer machine is like a car battery in that the potential power of the transformer field is finite, it's defined by the turns ratio and the primary input current.   This dictates the amount of "energy" present in the secondary side.   With no load, voltage is at it's maximum.   When you give the circuit a path to flow current, the voltage drops as current increases.  This curve is not straight due to ohms laws, etc.  more power  needs more current, but the total energy potential of the transformer is limited so it starts to drop volts.   Volts is often called potential in the electrical field.   Voltage isn't action, it's just potential that allows action (current).  Voltage will always be at it's maximum in a transformer machine with no current flow (open circuit), same as a car battery.I don't know how this is designed in an inverter machine because electrically they can make it do whatever they want with the right design, but they probably make it follow a similar curve.  Voltage doesn't' weld, current does, so they probably make it emulate the transformer.  Voltage allows the current to initiate, and to sustain arc, so it does need to be considered.Last edited by Chad86tsi; 03-11-2018 at 12:17 PM.
Reply:Cbad86tsi - Inverters have a generally vertical line unless "dig" is involved. https://www.millerwelds.com/resource...ining-purposes

Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Having voltage adjustment on the miller is definitely something I miss. Lincoln definitely had it right.Last edited by Burnt Glove; 03-12-2018 at 09:10 PM.Operating Engineers Local 3Lincoln SA 200Victor TorchDewalt Grinder10 lbs SledgeWhat more do ya need!


Reply:

Originally Posted by Insaneride

OCV or Open Circuit Voltage is what the volts are before you strike an arc. If using CC (constant current) then voltage will drop when welding. If using CV (constant voltage) then volts wont drop much if any but current will fluctuate. You said its a MILLER and I guess it has a CC and CV mode. Was it in CV when welding with 6010. BTW, hows the new job? Im sure as beautiful as it is driving thru the Sierras, it gets old.
Reply:I realize now that 70 volts was to high for CV but it was the first thing I thought when you said OCV's didnt drop. The OCV may not have dropped at 80 amps if that MILLER pipe pro is a bad boy welding machine. Be happy its not a BOBCAT.THORTON made that video in post #2. I think he was asking questions like yours before he made it. Check out his thread with similar questions. Hes the King of old LINCOLNS.http://weldingweb.com/vbb/showthread.php...ing&highlight=I know more about electricity than about welding. Higher volts allow longer arcing without snuffing like for the xx10 type rods. Thats in part why you turn up FINE volts (OCV) on your SA for 6010. You know all about the welding so good luck with the new Pipe Pro.On a side note: I was playing with my INVERTEC and LN22 feeder. A weldor that was helping me dial it in helped me learn something. That is; the wire feed speed affects volts when using CC. The OCV for INVERTEC is 69volts. That would always slam the 40 volt max meter on the LN22 but with correct wire feed speed, volts on meter showed about 29 volts. I think wire feed speed affects amps on a CV machine.
Reply:On a side note: I was playing with my INVERTEC and LN22 feeder. A weldor that was helping me dial it in helped me learn something. That is; the wire feed speed affects volts when using CC. The OCV for INVERTEC is 69volts. That would always slam the 40 volt max meter on the LN22 but with correct wire feed speed, volts on meter showed about 29 volts. I think wire feed speed affects amps on a CV machine.
Reply:A DAB, thanks for your explanation. I value your take on welding. I know cv is better for volt sensing feeders but I only have cc machines. I tried my SA200 black face with the ln22 (nr202 wire), the inverter 250 and an old 1947 180 amp copper wound idealarc. The idealarc seemed to work best. The inverter second best and the sa sucked. On the sa, I turned ocv's as low as they could go on the sa (~40 volts) . From what you explained here and what I was thinking: need to turn volts up on the sa 200 and retry. Your opinion of inverters and cc with volt sense is understood but, the Lincoln invertertecs are made to run 6010 and tig and have suggested settings for 6010. The volt amp curve is superior to other inverters as most won't run 6010. My ahp alpha tig does have an advantage for TIG  compared to my Lincoln and I am sure Miller would blow the doors off for tig. My point is, the invertec works with voltage sensing feeders but I need to retry the black face with higher ocv's.Thanks again.
Reply:

Originally Posted by Oldendum

From the Lincoln Handbook of Welding and Design:


Lincoln SA200 manual:


Reply:Willie, welding RPM on an sa200 is fixed and therefore does not control voltage. Same for my bobcat engine. Although I'm sure this is likely not true of every engine drive. Where the volt/amp curve starts dictates welding voltage for a given amperage. It's in the diagrams. The manual says that using a low coarse setting, and a high fine adjustment setting gives a high OCV.Using a higher coarse setting, and the corresponding lower fine adjustment setting would give a lower OCV at the same amperage as above (overlapping).For wire feed process in general, amperage (wire feed speed) controls penetration, voltage controls bead width and height.

Last edited by MinnesotaDave; 03-14-2018 at 01:52 PM.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:I checked the Bobcat manual. They show several volt amp curves. Voltage seems to not vary over a wide range. The manual makes no mention of manipulating voltage by any technique but arc length. They do say for "best results" use a low range, and high fine setting rather than a higher range, and low fine adjustment. The fine adjustment is calibrated not in amps, but in percent of the coarse range. They don't mention if either adjustment affects voltage. I believe the Bobcat too is constant speed, governed for 60 HZ tool power I believe to be 3600 RPM. My obsolete Twentieth Century stick machine does have three ranges. I've never experimented much. I presume they are stages of voltage. Each has a different amperage range. Now you've got me wanting to try an old machine with voltage control. It certainly is important in MIG, It seems it would be helpful in stick mode.The Dynasty when used as a stick machine has a dig control. that is said to increase amperage to prevent sticking, nice on 7018. I don't think it'd be all that effective for weaving uphill, except that one could run at lower amperage without excessive sticking.Last edited by Willie B; 03-14-2018 at 08:05 AM.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:I know this is a few years old, but do you have a title and publishing date for the book that those figures came out of? Searching Lincoln Handbook of Welding and Design came up with nothing. Thanks.
Reply:Here   :  www.jflf.org/default.asp The James F. Lincoln Arc Welding Foundation is a non-profit organization in the United States dedicated to disseminating arc welding information and educating students of all levels on the art and science of arc welding.Airco 250 ac/dc Heliwelder Square waveMiller Synchrowave 180 sdMiller Econo Twin HFLincoln 210 MPDayton 225 ac/dcVictor torchesSnap-On YA-212Lotos Cut60D
Reply:Great, but which book specifically did those pictures come out of. The procedure handbook of arc welding design and practice does not have those pictures in the 1955 or the 2000 edition I was hoping to find that exact copy.
Reply:

Originally Posted by Burnt Glove

The way I understand it, OCV is what allows you strike an arc when stick welding. But what happens after you strike an arc and start welding? Does the voltage drop down? Does the voltage have any effect on the arc itself? I ask because watching one of our machines at work today, I noticed that the voltage on the display stayed around the mid 70's range (miller pipe pro 304). Guy was running 5/32 6010 5p at around 80 amps. Would like to better understand OCV's and it's effect while welding.
Reply:

Originally Posted by Novo Sibirsk

Great, but which book specifically did those pictures come out of. The procedure handbook of arc welding design and practice does not have those pictures in the 1955 or the 2000 edition I was hoping to find that exact copy.
Reply:

Originally Posted by Mike_L

Doh! I didn’t realize this was an old resurrected thread, I paid no attention to the date.I don’t know for certain, but that welder on one of the pictures looks similar to some I’ve seen from the 60’s. The older guys here could probably give you a closer date.

Originally Posted by farmersammm

Might be an oldie, but it was actually a goodie.  I ordered the Lincoln Handbook of Arc Welding and Design offa Ebay because of it.  I have the Bible, but I thought, after seeing the reference to this book, it would make a nice addition.
Reply:Without trying to understand all the information above......and injure my brain in the process:A specification of a inverter TIG reads: “Open circuit voltage (VRD active).  Last edited by Oldendum; 02-21-2021 at 11:21 AM."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Tighter fit "vertical down" needs to run hotter than loose fit vertical up. Not that most people do a lot of vertical down groove welds with 6010/7010 rod beside pipeline guys.Having dig control just helps fine tune your welds, but isn't an absolute necessity.Miller pipe pro 304 manual explanation:https://www.millerwelds.com/files/ow.../O492M_MIL.pdf Dig/Inductance ControlControl adjusts Dig when Stick mode is selected on mode switch.When control is set toward minimum, short-circuit amperage at lowarc voltage is the same as normal welding amperage.When set toward maximum, short-circuit amperage is increased at low arc voltage to assist with arc starts and help prevent the electrode from sticking while welding (see volt-ampere curves in Section 3-4).Select setting best suited for application.

Last edited by albrightree; 02-21-2021 at 10:00 PM.Airco 250 ac/dc Heliwelder Square waveMiller Synchrowave 180 sdMiller Econo Twin HFLincoln 210 MPDayton 225 ac/dcVictor torchesSnap-On YA-212Lotos Cut60D