Squirrel cage induction motor, construction, working principle and applications
Squirrel cage induction motor is that AC induction motor type which function is based on electromagnetism principle.
Why the name squirrel cage induction motor ?
This name of squirrel cage motor comes from the fact that the rotor of the motor looks like the cage of a squirrel (squirrel-cage rotor)
Squirrel Cage Induction Motor structure
This motor has main four parts
- Stator
- Rotor
- Bearing
- Fan
Stator of 3 phase squirrel cage
Stator consists of a three phase winding (usually made of copper) in a core and metal housing.
Windings are made of copper or aluminum and are mounted on a laminated iron core to provide low reluctance path for generated flux by AC currents
Rotor
The rotor is that rotating part of the motor to provide mechanical output, It consists of a shaft, core and short-circuited (copper) or aluminum bars
Fan
TEFC (totally enclosed fan cooler) squirrel cage induction motor has a fan mounted and fixed on the rotor shaft to draw air on the motor surface to cool it down
Bearings
Bearings are used to provided a base for rotor motion, and keep the motor rotation smooth
Squirrel Cage Induction Motor principle of working
A rotating magnetic field is produced in space when power supply is given to the stator winding, The speed of the field which is known as the synchronous speed
Short-circuit current start flowing in the bars of the rotor due to the magnetic field, and produce A self-magnetic field which interact with the stator field.
Now rotor starts following the stator rotating magnetic field trying to oppose its cause, and the rotor rotates
Motor applications
Three phase induction motor is the most widely used motors in all industries and electrical applications
They are suitable for applications like:
- Oil and gas pumps
- Centrifugal pumps
- To run conveyor belts
- Large fans and blowers
A dvantages
- High efficiency
- Low cost
- Requires less maintenance compared with slip ring motors (no brushes slip or rings)
Disadvantages
- High starting current
- Low starting torque
- Speed control is poor
- If supply voltage is reduced, the motor draws more current
