There is a wide range of applications of induction motor in Industry as well as in daily life. because of its simple design, rugged construction, and reliable operation. induction motors have easy operation and simple maintenance, low initial cost, high efficiency, and availability of different starters. For starting loads such as small refrigerating machines operating at full pressure or conveyor belts motor with high starting torque induction motors are used. Almost 90% of motors in the industry are induction motors
The applications of the induction motor are distinguished by the type of rotor used.
1) Squirrel Cage Rotor application
2) Slip Ring or Wound Rotor
The loads which required low starting torque and throughout constant speed, squirrel cage induction motor used. Squirrel cage induction motors are designed with low rotor resistance or with high rotor resistance. The low rotor resistance motor gives poor starting performance but better running performance on the other side squirrel cage motor with high rotor resistance gives better starting condition and low running performance.
The squirrel cage electric motor with low rotor resistance (FL Slip 3 to 5%) are mostly used for fans, centrifugal pumps, etc. and the other motors with high rotor resistance are used for compressor and crushers. Cage motor with higher rotor resistance used for loads like punching machines, hoists, and elevators. These are applications of squirrel cage induction motor.
Slip ring induction motor(Wound Rotor) finds application for loads requiring more starting conditions and also loads that requiring speed control.
A slip ring induction motors are more expensive than a squirrel cage type and require more maintenance because of brushes and slip rings.
Slip ring induction motor mostly used in the application of hoists, cranes, elevators, and compressors. By the use of a wound rotor or squirrel cage rotor with a suitable controller and external resistances connected in series with the rotor, it is possible to obtain any value of starting torque.