I have a lincoln 175 and a plasma cutter that I run off of 50' of 10/3. I just went down to Lowes and bought the commercial grade heavy duty 10/3 and cut the plugs off and put on the plugs I needed for my welder and dryer outlet. You should be fine with some 12/3.Its probably rated 15amps because of the plugs.
For wire size check out this link.
http://www.elec-toolbox.com/calculators/voltdrop.htm
