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 program and the energy requirement in most 
of the houses, shops, offices are little, which can be very easily met by a speed reducer single 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 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 brief the rotor conductors called the end rings.
To provide mechanical power, these rotor conductors are braced to the end ring and hence form a complete closed circuit resembling a cage and therefore got its name because 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 level of resistance as the bars get completely shorted. The absence of slip ring and brushes make the building of single stage induction motor very easy and robust.