For a phase converter to generate three-phase power, the two incoming power line are directly passed through to the output and the phase converter generates the third leg in a configuration know as "high-leg delta." This will power most three-phase machines. Some machines however, require wye-configured power, which includes a neutral. If your machine requires wye-configured power, you will need to send the output of the phase converter through a delta-to-wye isolation transformer before going to your load.