Putting the sting in stinger with 125ocv reading.

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Dialing in the DC side of my 220volt frankencraftsman today. I was amp clamping, OCV testing and burning some 3/32" and 1/8" 6011.On my lowest settings I'm getting about 125dcv, on the higher settings its 90dcv to 110dcv (all ocv readings).This happened after I added a 150v 550uf electrolytic cap. I figured as much before hand, I was getting 86dcv before with out a capacitor, thanks to RMS.The arc strikes up real nice now with the cap so it stays.Also the DC amps are tracking with the amps listed in the AC amp selector. DC amps are only about 4 or 5 lower than the AC lable, my guess is its lower from going through the extra cable length and inductors.I also found this machine draws almost 4 amps at idle. Wiring the fan to run all the time on its own switch looks like a really good idea. Before I put down the stinger I always switch the transformer power off. Apparently that really cools the transformer off good. I flog it pretty hard and it barely gets warm.All the modern solid state stuff reads around 50dcv with no arc. So naturally 125vcd seems a bit excessive.Is 125dcv too much?old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:I searched around some more and it looks like nomal DC, OCVs are well under 90v  .old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:Originally Posted by mad welder 4I searched around some more and it looks like nomal DC, OCVs are well under 90v  .
Reply:Hello mad welder 4, higher OCV's allow for easier arc starting, the problem with the higher OCV's amounts to a need for a threshold of safety. At those volt levels you are pushing what would be considered "safe". Think in terms of welding in the rain or a moist environment, with that voltage level a "shock" could amount to more than just a simple nuisance. So at what point is safety traded for stupidity, that is a personal call when you are building your own equipment and setting the OCV level. I am not saying that you are stupid at all so please don't misunderstand my comments. Industry is certainly going to limit their OCV levels to a point that is well below what would be considered dangerous. What an individual does is their own choice. That's my $.02 here. Good luck and best regards, Allanaevald
Reply:If you took a 220v welder that was rated at 80v ocv,and fed it 244 it should end up about 90v ocv,so nothing too strange there.
Reply:Originally Posted by BlueweldersIf you took a 220v welder that was rated at 80v ocv,and fed it 244 it should end up about 90v ocv,so nothing too strange there.
Reply:Not too worried about moisture here.We get precipitation maybe 10 days a year, half those are snow days.I was checking over stingers (there a 3 in my collection) with a fine tooth comb since I know 125ocv can be a bit hazardous and found my hobart stinger has an exposed screw head, completely defeating the propose of the insolated stinger. Guess I will wrap it with lots of electrical tape.I fired up a slightly used 1/8 inch "7018 1" on DCEP and it started great, did a few tack welds burned the rod 3/4, restarting real easy each time then went to restart again and stuck the rod and it became hard as hell after that to restrik the arc i think sticking that rod some how killed the capacitor. OCV were down to 70 to 80 vdc when I rechecked it with a multimeter.Looks like I will be taking it apart again..EDIT: The lead was burned off the capcitor, its repairable,  but think I need to find a heavy duty capacitor with screw ends.Thats a pretty serious amout of power going in and out of that capacitor to melt that lead off. Last edited by mad welder 4; 02-19-2014 at 10:03 PM.old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:I am sort of surprised that a 550uf capacitor would have cooked a lead off.
Reply:Its about as dangerous as an exposed 120vac wall socket.  That's more than enough to shock you if you touch both ends with dry skin. With wet skin, or if it punctures you somehow, it could kill you. Be careful. Modern inverter stick welders are a lot less than 50v OCV, more like 5-10v.Welding/Fab Pics: www.UtahWeld.com
Reply:I replaced the 550uf 150v cap that had scrony 20ga or 22ga leads with a salvage 1000uf 200v with snap in leads. I would have preferred a lower uf cap but didnt have anything more than a 35v rating.Of course with no circuit board to snap into I just soldered 16ga wires into the snap in nubs and wire nutted them onto the rectifier output harness. I dont plan on using the 1/8 inch rod settings with the insanely high ocv very often. If I can weld it with an 1/8 inch rod thats likely mig territory.  Since all my 1/8 inch rods are AC compatible I can always switch over and run AC at a normal ocv.old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:The capacitor is placed in between the rectifiers and output choke.Did it that way because almost anything I have seen that uses a capacitor and inductor to smooth out put is wired that way.I will test out the larger capacitor today and see how it does, I have a feeling I will want a much smaller one in there.I can always go in and rewire the capacitor on a switch.My multi meters are fluke 87, 123 and 325. The 325 is brand new. So they are pretty accurate.old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:I think you will find that a smaller capacitor around 50uf with the appropriate dc voltage and a bleeder resistor will give you the best best stability on a CC machine. A similar sized AC capacitor before rectification may help as well.Any larger in my experience will lead to anything from literally blowing the tip of the electrode(2000uf) to a gradual voltage drop with smaller capacitor values(≈500-1000 uf) that will make welding a longer bead difficult.Smaller capacitors with help smooth out the AC ripple and give some stability but not be so large as to cause other issues.Last edited by kald; 02-20-2014 at 10:53 AM.Idealarc 250AC 225SVictor OA-older made in USA stuff.And a crap ton of other stuff.
Reply:Prerectifier AC caps will be small, non-polarized caps. AC capacitors always have much lower uf rating than similar size electrolytics.I will start searching for a much smaller output capacitor, I figured 500uf was about the upper most limit.My bleed down resistors are a light bulb. It bleeds off the cap, lets me know the DC side is hot and provides light for low light situations.old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:I just realized I have 2 of these 1000uf 200v capacitors, if I serries them up that will cut the capacitance in half. At least I know it works reasonable well with 500uf from the last capacitor.I ordered two 47uf 200v electrolytic caps, but they will take a week to get here.old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder