Power fluctuations affecting my tig welding?

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Hi all, I am trying to learn tig welding at a votech school.  One problem I'm having or at least I THINK I'm having is that power fluctuations are causing my machine to run cold midway through my welds.  I usually start the machine out at about 120 amps, and I'm using 3/32 " filler wire.  I am making fillet welds. I also had this same problem while making simple weave beads on a plate.  I think it happens when a lot of other students are using their welding machines and various other machines in the shop. I think that's when my machine starts to go cold. Also I've noticed when the shop is relatively empty, I am able to make more consistent welds because the heat stays high and I can manipulate the bead better.  What do you think?  Is the problem just my lack of skill and I'm blaming the machine or is power fluctuations due to high use of shop equipment a likely problem?  Do experienced welders encounter this sort of problem regularly?  Any suggestions or information would be most greatly appreciated.  Thanks.
Reply:Hey guideseek,Yes, that is a possibility. A load center is designed with a maximum input current rating per circuit number & output current needed. If your load circuit is at minimum current usage, then you will have the required input amperage per your units' demand at that setting. The more current used by other units will decrease your input current a bit. You may have to adjust to a higher setting or more pedal to retain your level of output. The only test you can do would be with a load tester at the circuit/breaker location & watch the fluctuation as successive units are being operated.DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:If you can get a good voltmeter that will work in a high interference environment, you could watch the voltage coming into your welder, as activity changes in the school.I am not sure how much variation would cause problems, but voltage variations in excess of 5% are not good, as I understand electric power systems.Not sure if you have tried a different welding machine, or if they all behave the same.A clamp on ammeter could be used on the welding leads to measure the current flow.  You could clamp the stick lead to the ground lead, set the current at 50 amps, and watch the current variation.  Any decent welder should survive a short circuit at low current, as I understand it.  Tig and stick welders are constant current, more or less, so will limit the current even into a dead short.  Measuring the current while welding is too variable to be terribly useful, I would think.If I think about current settings on my welder, 10% more current often makes a pretty big difference.  I don't think that I could detect 3% variations in current, but not sure.  To some extent, you could compensate for machine variation with the foot pedal, but that adds more complexity to an already complex task, Tig welding.RichardSculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge