Three-phase gets really weird when you talk about solar cell interfaces. Best to avoid them.
But even two-phase can be problematic. If you lose one phase of supplied power, the other phase can burn out motors which don't have circuit interruption. The way to protect the motor is to route its power through a contactor whose activation coils depend on each phase in turn. If any phase drops out, the contactor opens, protecting the motor.
Yup. And your appliances have to be gentle about getting low voltage, because the voltage between the legs is 207V. It’s been a long while since I had to mess with residential wiring, but that seems to be the case.
(I really hate it when a neutral breaks loose, but that a whole other deal...)
You betcha! That's why they make 'phase protection' circuits. Very important thingies to have in NYC because Con Ed has a nasty habit of flipping phases if they do some work out on the street where your feed comes from. Since phase protection has not always been in the code, a lot of old stuff, of which a lot is AC motored, has no protection from this. So elevators go up instead of down and ventilation equipment sucks instead of blows..
Now a quiz question. In your normal house service, you have 240 ac (or 220, or 208) coming into the house. If you go from one leg of that 240 vac feed to ground (neutral - which in most places is grounded, but not always..) you get your nominal 120 vac house voltage. Here's the quiz question: What is the voltage to ground/neutral from one leg of a 480 vac three phase supply?
Bonus question: Assuming the wiring follows code, how can you tell whether you are looking at a nominal 240 three phase or a nominal 480 three phase feed without a meter or looking at the name tags.. (and no, not by grabbing one of the hot wires and grounding yourself..)