Input PowerRequires 1-Phase Power?

Question:is the the info i need or is there more i need to find out . also can i replace other brakers with 120 half to make room for 20 50amp breakers

Answers:
all power in USA is 1 phase or 3 phase.if 1 phase 220 volt you will have 2 hot lines and one neutral and one ground wire supplying power to main breaker box.if 3 phase 220 you will have three hot lines and one neutral and one ground wire supplying power to main breaker box.you will have to give more information about what you want to do about breakers as your question needs clarifying.why do you need twenty 50 amp breakers...what do you mean by 120 half