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Suppose the heater is wired as three resistors connected in a wye, then those resistors can be connected in parallel and fed single phase from 220 V. The resistors are probably the major power load.
Thus, any real three phase loads are probably small. A small rotary converter could be used for their power, or a VFD run at fixed frequency, or a capacitor type phase shifter (which I don't like).
A rotary converter is usually just a three phase induction motor fed from single phase, and a start capacitor to get it started, and provide some addition phase shift current path from the ingle phase source. Or you can use a pull cord to start.
A synchronous three phase motor is either a motor or an alternator depending upon how it is loaded. This is probably a better phase converter, but more expensive than an induction motor. Or you could use a single phase motor to mechanically drive an alternator. This could be a good way if you needed a frequency conversion which would be accomplished via the belt drive ratio.
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