# Understanding the relationship between thc and live voltage

Im pretty sure i have seen a post that goes into detail on how the touch off effects the live voltage, followed by discussion on what typical live voltages were on different material thicknesses.
I was still at a more basic level of knowledge and the information was not something that i needed at the moment [ small brain of mine needed to focus on other issues lol ]

Well now id very much like to read that post and cant for the life of me find anything about the nity gritty of how they relate , let alone that post. Anyone help steer me in the right direction

Thanks

I think this covers it. You wonâ€™t be able to adjust the voltage yourself. It will be relevant to the amps. For example, when you have the ground interference, the live voltage is way too low. So it pierces, but itâ€™s reading at around 30v. THC tries to compensate by raising the torch, but it canâ€™t go high enough to hit the target voltage so you get crappy cuts/ no cuts.

Voltage depends on torch height and arc length. Even telling firecontrol your target voltage is 120 wonâ€™t guarantee it hits it.

I reserve the right to be wrong, and will accept any correction given.

I have read that, and will do so again. But i donâ€™t recall it taking about expected values.

Iv gathered that the torch height affects voltage but thought i remember a post that got into the mechanicâ€™s of it all.

What triggered me looking for more info was not seeing a significant difference in the live voltage between cutting the 16g i have been using lately and some 3/16 i cut last night. Both were about 86volts

The voltage depends on many factors, but is a relatively strong function of the distance to the top surface of the material and depends only weakly on thickness assuming you are cutting at the proper speed. Thus seeing little difference between 16GA and 3/16 should not necessarily be a surprise. Looking at the cut chart for a Hypertherm 45, the cut voltage goes from 128 volts at 16GA to 129 volts at 3/16.

So if im consistantly getting lower than book spec voltage should i adjust my price height and cut height/ feed rate to get closer to nominal? When i pierce at .125 and cut at .04 [ sheilded consumables] or .150 and .065 with my unshielded stuff i consistently get a live voltage between 88- and 92 . My cuts looks decent and consumables seem to last on par with what others have posted. If i was not aware that my voltage was low i would not be looking to fix anything, but knowing its low bothers me . At the same time i donâ€™t what to cut at .085+ or .2 pierce just to get my voltages in check.

You should treat book values of cut voltage as a guide, but you should run at whatever cut voltage you measure on your machine when cutting at the proper speed and height. In other words, cut voltage should only be used to maintain consistent cut height during a cut, but not used to set it.

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