Induction Motors

Induction motors are termed "induction" because there is no current supplied to the rotating coils. The coils are closed loops which have large currents induced in them by the changing magnetic field produced in the stator coils.<ref>http://hyperphysics.phy-astr.gsu.edu/HBASE/magnetic/indmot.html</ref>

There are two main types of induction motors.

The first type is an adjustable-speed drive. These are used in the process control industry to adjust the speed of fans, compressors, pumps, blowers, etc. Also, these are used for electric traction in hybrid vehicles.

The second type is a servo drive. These emulate the performance of a DC-motor drive and are used in machine tools, robotics, etc.

Squirrel-Cage Induction Motor

These are commonly used in adjustable-speed applications. The cage has bars of copper or aluminum running the length of the rotor. In most working motors, the bars are skewed from following the axial direction of the motor perfectly to reduce noise. The bars are shorted at each end of the rotor by end rings, and thus producing a cage like structure.

References:

Induction Motors