I am a bit confused on some of the terminology being used and the possibility of different voltages in different countries, but physics work the same all over the globe. Ovens that work on 220 american should be called single phase 220v because they derive there source from two hot 120 volt sources that combine send 220v to the load. Two phase is an old antiquated system that was popular years ago which had a 90 degree out of phase relationship. The bottom line is that any element (load) is a resistive source that stays the same no matter what the voltage applied is. Because of this the current will drop in a direct linear relationship. Without getting to technical the wattage ( heat ) is a direct relationship to the square of the current times the resistance. I squared x R. Bottom line is, if you cut the voltage feed in half you will only get about 25% of the heat.
I may not understand what you meant about hooking it up to one phase and melting the breaker. The current will not go up when you add less voltage because the resistance stays the same. The current will be less.
Even in a three phase unit the applied voltage drop has the same effect.
My technical english is poor in using the right words, you are right.
So maybe i understand you not that good.
But you are right about the voltage in relation to resistance.
I live in Holland, here we have 220volts, and 3 fase is in that way 380.
This oven is ment for 220/380, the elements are both around 20 ohm. (in the states it must be 10 ohms)
If you buy a oven in the states you can do this trick also with lower voltage and more amps, same power (P=U*I).
The wireing is as thick as here but with a lower voltage you can send more amps through it.
The colour code of electric wire is also some differend aroud here, or there.
It has noting to with fase differance 120 or 180 degrees by the way, i know what you mean.
Both elements must have 220 volts, 380 volts is between fases.
I measured my oven with a good ohm meter, internaly it must be connected in the way i drawed.