We utilize the single-phase power program more widely than three phase system for 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 power requirement in most of the houses, shops, offices are little, which can be quickly met by an 
individual phase system.
The single phase AC motors are further classified as:
Solitary phase induction motors or asynchronous motors.
One phase synchronous motors.
Commutator motors.
The squirrel cage rotor contains aluminum, brass or copper bars. These aluminum or copper bars are called rotor conductors and placed in the slot machines on the periphery of the rotor. The copper or light weight aluminum rings permanently brief the rotor conductors called 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 as squirrel cage induction engine. As end rings completely short the pubs, the rotor electrical resistance is very small in fact it is not feasible to add external resistance as the pubs get completely shorted. The speed reducer absence of slip band and brushes make the construction of single stage induction motor very easy and robust.