We use the single-phase power program more widely than three phase system for domestic purposes, commercial purposes and some extent in commercial uses. Because, the single-phase system is more economical than a three-phase system and the power requirement in most of the homes, shops, offices are little, which can be easily met by an individual phase system.
The single phase AC motors are further classified as:
One phase induction motors or asynchronous motors.
Solitary phase synchronous motors.
Commutator motors.
The squirrel cage rotor consists of aluminum, brass or copper bars. These aluminium or copper pubs are called rotor conductors and placed in the slots on the periphery of the rotor. The copper or aluminium rings permanently short the rotor conductors known as the end rings.
To provide mechanical power, these rotor conductors are braced to the finish ring and therefore form a complete closed circuit resembling a cage and therefore got its name as squirrel cage induction engine. As end rings permanently short the pubs, the rotor electrical level of resistance is very small and it is not feasible to add external resistance as the pubs get permanently shorted. The lack of slip band and brushes make the construction of single phase induction motor very simple 
and speed reducer robust.