Bill - as a follow-up to your post..... My compressor is on a dedicated 220 service in the shop (the compressor is screwed to the floor) but I wired it with a dryer-type plug. With 100 amp service in the shop I can easily unplug the compressor and plug in the 30' extension cord to the welder (I forget the wire gage but it's significant and heavy!) and run the welder pretty much anywhere in the shop. Works great. There isn't enough power in the shop to run the welder and the compressor at the same time along with the AC and other power tools and this way I CAN'T screw up and do that. So I think you've done exactly the right thing.

Dan