Question for Thunderbolt experts....

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Regarding my Thunderbolt XL....on a.c. you have a choice ofa normal or high range.For instance:  If I want to use 160 amps a.c., I can use the normal range and crank the crank up to 160....OR use the high range, and crank the crank down to 160.Question #1:  What effect (if any) does this have on the arc ?Question #2:  Can I use it in the high range and crank it down to a lower amperage setting, even though it's not marked on the dial ?    THANKS !I'll be the LAST one to let you down !
Reply:Markopolo,  on almost every type of machine I've ever used the manufacturer has recomended that on tap or range set machines,  you should use the lowest  tap or range and set it at the higher percent setting.  This goes for Mig, Tig or Stick welders.  Your welder wil perform more efficently and should have better arc characteristic at these types of settings.  In other words, on your Thunderbolt , use the normal range and crank it up to 160 for best results.
Reply:Marco:I disagree with "Docwilson". You want to use the setting that will give you the highest "duty cycle".Years ago when I had my old "Sears Buzzbox", it had two ranges. If I'd  weld at 100 amps. If I remember right,  the low range went to about 130 amps, the hi range went to 235. 100 amps on the lo range had about a 40% duty cycle. 100 amps on the hi range had a 100% duty cycle. My memory is a little foggy on the actual settings, but you get the idea.Look at your owners manual at the amps/duty cycle chart, and you will see what I mean.
Reply:I thought the different ranges also changed the OCV. I don't know, might just be the voices talking to me again.My big, old Airco has 2 ranges but no owner's book. I can't wait to see some more info on this.If the voices are right, speaking of SMAW, what would different (higher and lower) OCV's do?MillerMatic 175Thermal Dynamics Drag-Gun PlasmaAirco Bumblebee AC/DC SMAWVictor Super-Range II oxy/act
Reply:"Ohm's law", the higher the amps, the lower the "OCV"
Reply:A good reference for this is Millers "Basic electricity book", from their "Student package".
Reply:I've been meaning to get one of Miller's student packs. Maybe time I get one.Thanks to you for reminding me of Ohm's law I now see the simple relationship of voltage and current in a constant current SMAW machine.Depending on how the transformer is wound, different OCV's could be achieved. Any idea on what the differences would be. I'm not near my machine and don't remember my machines OCV.Last edited by malibu101; 05-13-2004 at 11:13 AM.MillerMatic 175Thermal Dynamics Drag-Gun PlasmaAirco Bumblebee AC/DC SMAWVictor Super-Range II oxy/act
Reply:I think the Millers/Hobarts have the selling point that their duty cycle is related to welding current, and therefore they offer longer duties at lower amperages.  Perhaps this was not available on the older Sears-type models, which is why Miller/Hobart would make it a selling point.My gut tells me there's no difference.  If you KNOW you need 160A, and you can get it from either range, then it shouldn't matter what range you were on.It's probably more for convenience in adjustments at this point.  Be in the range that will allow you to adjust the machine throughout that project without having to switch ranges.The ranges are there because it makes for a simpler / cheaper xformer design.
Reply:Mac.It all falls back on ohm's law. a transformer is a transformer. The Thunderbolt is a variable core (Reactor) transformer, just like my old craftsman was. I looked at the manual, they don't seem to have any phase correction inductors, or capacitors. Just transformer, and rectifier. I believe when your on the high range tap on the transformer, the "Reactor core is cranked back. This gives you less inductive reactance, and eddy currents in the core, this translates to less heat, which means a higher duty cycle.Marco:Try this experiment. If you have a thermometer set it on top of the welder. weld ot a max low tap range for a period of time. Check the temp.  Allow the machine to return to ambient temp. Then switch to the high range at the same amps. Weld for the same period. I believe, you'll find you have a lower temp at the high range. Lower temperture = higher duty cycle.
Reply:I have a big 1976 era Airco Bumblebee stick machine. It seems exactly similar to Miller Dialarcs of the same era. It has a huge cooling fan. Granted I don't do ultra high amperage welds or weld for extended periods of time. In fact I seldom stick weld other than for the fun of it  But, I have puposely felt the cooling air and the machine when it was used it's hardest since I've had it, and, I felt no heat. Which is a good thing.  This huge lump is WAY more stick machine than I need but the price was right and it'll do anything I'll ever need.Again, thanks for the info!Last edited by malibu101; 05-13-2004 at 12:37 PM.MillerMatic 175Thermal Dynamics Drag-Gun PlasmaAirco Bumblebee AC/DC SMAWVictor Super-Range II oxy/act
Reply:Marcopolo you can use either range for 160 amps but when set in low range you have a higher voltage available which will help light the stick easier. This extra voltage also helps to keep from sticking to the plate while welding. Tank
Reply:This was such a good question, I asked Miller.  Here's the answer:MAC702, The only difference you will see between the high and low tap is a slight difference in open circuit voltage. The low tap has a higher open circuit voltage than the high tap. Basically, you are just adding/subtracting a few turns on the secondary when you switch ranges (high/low). With that said, it is not enough turns to make any difference in duty cycle. What ever the duty cycle is for 160A, it is the same in low range as it is in high range. Any other questions, post back. Hope this helps.__________________Brian [email protected] edited by MAC702; 05-13-2004 at 03:34 PM.
Reply:I'm sorry if I stole this thread, but, thanks for the info!I also see the voices in my head were right.MillerMatic 175Thermal Dynamics Drag-Gun PlasmaAirco Bumblebee AC/DC SMAWVictor Super-Range II oxy/act
Reply:Looks like ITW has cut down on their winding quality. I guess high and low taps is just a marketing ploy. If the duty cycle isn't affected, OCV can't be affected very much either. It's a law of nature.
Reply:Jim the little Miller sticks have been like that for years. My grandfather had one that was made in 1971 and it was the same way. High range had lower voltage than low range did. Tank