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 program and the energy requirement in the majority of the houses, shops, offices are small, which can be quickly met by an individual phase system.
The single phase AC motors are further classified as:
Single phase induction motors or asynchronous motors.
One phase synchronous motors.
The squirrel cage rotor consists of aluminum, brass or copper bars. These light weight aluminum or copper bars are known as rotor conductors and speed reducer positioned in the slot machines 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 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 level of resistance is very small and it is not possible to add external resistance as the pubs get permanently shorted. The lack of slip ring and brushes make the structure of single stage induction motor very simple and robust.