What is Overload Rating, constant torque, and variable torque? 

I am a retired sparky who worked on drives for 30 years. Best drives were those not made in cheating lack of quality control communist china. My favorite drive compamy was Danfoss due to quality products great tech support and eady to get spare parts. Allen Bradley are great. Went to a drive class grom them for a week. Hated prima donna ABB. Would always give me run around.

Leslie, are you asking if you can use a VFD with your induction heater? If it has an electric motor, yes. You will need to derate a 3 phase to 3 phase VFD to use with single phase power. Meaning you need a VFD twice as big as your motor, so about 40kVa (32kW / 42HP). Use your motor FLA as a measuring unit. Hope that helps.

do i really need to run a motor to produce the third charge and are capacitors essential as well? i'm guessing induction heater produces amps at about 17mv not sure what that means but the volts are 300-500v, still learning, sure wish a switch board could do that or safety plug, is it true that nz electricity is far to high voltage, or do i need a safetey trip switch, what is the wall unit that converts single phase wall plug of house over to amps AC? or do i just use a DC / ac inverter? because i don't want to use petrol or ./diesel i hear induction heaters can run on 1kva does a electric motor serve as alternator ac producer as well as motor running, i'm sure it's more about charging big capacitors, i won't know until mid year tbh

isn't there supposed to be a trasnformer infront of the motor?

what does a vfd do again?