Thank-you for the detailed information Eric.

I plan to use 1-1/2' conduit and bury a phone line and water line, all
36" deep while I am at it. The writing on the wire is RW90 XLPE 1000V,
which is moisture resistant as far as I can tell from a quick web search.

Does the 2% voltage drop current of 17A mean that I should fuse the
sub-panel for 35A if I use 2 conductors? I was hopeing to get 50A. My
high current loads are the welders which I operate at low duty cycles.
since this is just a hobby shop there is never more than one big machine
working at once.

stan