How to connect single-phase appliance to 240v feed?
If you're not using the neutral, you should have a NEMA 6-30 receptacle instead of a NEMA 14-30.

Other than that, it looks like you're all set. The black wire is one line (L1), the red wire is another line (L2), and green is ground.  You should have 240 volts between L1 and L2, since you have a 120/240V single split-phase system.  

You don't have to worry about the three phase warnings, since you don't have a three phase system.