An overseas company is making a machine for me and they need to know whether I want 1,2 or 3 phase and what voltage
"out of your element" .. okay. Heating elements are most of your power and 30A at 240VAC is 7.2kW. 

I think 240VAC/60Hz is what you want. Three phase power is going to restrict you to industrial units in many cases, and is very expensive to get installed if it does not already exist. Some commercial buildings use 208 3-phase, which yields 120VAC naturally, but there's not a lot you can do about that if you don't know where you are going to put it eventually. Usually 240V devices will operate okay, but with noticeably (~25%) less power, on 208V.  

As to whether it's single phase or so-called two phase ("split-phase" is the proper term), having the neutral and two hot wires, as your major appliances in Canada have, might allow them to use some 120VAC components. It might be best to send them a little diagram of what your receptacle wiring looks like. Something like this:  (borrowed from this website. 

Don't forget to specify 60Hz. Much of the world uses 50Hz.