We utilize the single-phase power program more widely than 3 phase system for domestic purposes, commercial purposes and some extent in industrial uses. Because, the single-phase system is more economical than a three-phase program and the energy requirement in the majority of the houses, shops, offices are small, which can be easily met by a single phase system.
The single phase AC motors are further classified as:
Single 
phase induction motors or asynchronous motors.
Single 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 positioned in the slot machine games on the periphery of the rotor. The copper or aluminum rings permanently short the rotor conductors known as the end rings.
To provide mechanical strength, these rotor conductors are braced to the finish ring and hence form a complete closed circuit resembling a cage and therefore got its name as squirrel cage induction engine. As end rings permanently short the bars, the rotor electrical resistance is very small and it is not speed reducer possible to add external level of resistance as the bars get permanently shorted. The lack of slip band and brushes make the structure of single phase induction motor very simple and robust.