We utilize the single-phase power system more widely than 3 phase system for speed reducer household purposes, commercial purposes plus some extent in industrial uses. Because, the single-phase system is less expensive than a three-phase system and the energy requirement in most of the homes, shops, offices are little, which can be quickly met by an individual phase system.
The single phase AC motors are further classified as:
Single phase induction motors or asynchronous motors.
Solitary phase synchronous motors.
Commutator motors.
The squirrel cage rotor includes aluminum, brass or copper bars. These aluminium or copper bars are called rotor conductors and placed in the slots on the periphery of the rotor. The copper or light weight aluminum rings permanently brief the rotor conductors known as the end rings.
To provide mechanical strength, these rotor conductors are braced to the end ring and hence form a complete closed circuit resembling a cage and hence got its name since squirrel cage induction motor. As end rings completely short the pubs, the rotor electrical resistance is very small and it is not feasible to add external 
resistance as the bars get completely shorted. The lack of slip ring and brushes make the building of single phase induction motor very easy and robust.