We use the speed reducer single-phase power system more widely than three phase system for household purposes, commercial purposes plus some extent in commercial uses. Because, the single-phase system is more economical than a three-phase system and the energy requirement in the majority of the homes, shops, offices are small, which can be very easily 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 aluminum or copper pubs are called rotor conductors and placed in the slots on the periphery of the rotor. The copper or aluminum rings permanently brief the rotor conductors known as the end rings.
To provide mechanical power, these rotor conductors are braced to the end ring and therefore form a complete closed circuit resembling a cage and therefore got its name as squirrel cage induction motor. As end rings permanently short the pubs, the rotor electrical resistance is very small in fact it is not feasible to add external resistance as the pubs get permanently shorted. The absence of slip band and brushes make the construction of single phase induction motor very easy and robust.
