Squirrel cage induction motors is one of the most use type of motor in electrical engineering. These three phase induction motor can basically classify according to its construction feature such as.
- Squirrel Cage Induction Motor
- Wound Rotor Induction Motor
According to these two motors, Squirrel Cage Induction Motor type are widely use because of it cheap and also got rugged construction so less maintenance is use .The stator of mentioned both types of motor are same but the construtction of the rotor is differnt.
Construction of the Motor
The rotor of Squirrel Cage Induction Motor contains a cylindrical core and the rotor core also consists lamination to reduce the eddy current effect like electrical transfomers. The rotor also consists two copper bars which short-circuited with each other. sometimes for cooling purposes the rotor also consist fan.rotor is include heavy copper or aluminum bars which are insert form both ends and the ends are short-circuit with cylindrical copper rings. These copper rings are also connect at the end of the rotor and it looks like a squirrel cage so its name as squirrel cage type rotor.
Squirrel Cage induction motor working principle
When balanced three phase voltage is apply to the terminals of the windings, it produces rotating magnetic field in the air gap.
This magnetic field having a sinusoidal special distribution and rotating constant angular speed. This field is now sense by the rotor and is three phase winding is then induced with a balanced three phase voltage.
The rotor is got close windings and due to this, a balanced three phase current is established. So the interaction between the rotor current and the air gap flux produce torque is the reason to rotate.
rotating field of the stator is pass through the air gap of the induction motor. When the stator field rotates it cut the rotor conductors which is stationary.
Due to the relative speed between the rotating flux and the rotor conductor emf induced. When the rotor conductors are short-circuited the current will flow through the rotor conductors.
The current produced in the rotor conductor lead magnetic field produces in the stator. The current produced in the rotor conductor lead magnetic field produces in the stator.
There is a mechanical force act on rotor conductors and the total mechanical force of entire rotor conductor create torque. This torque leads to move the rotor in the same direction of the stator rotating magnetic field.
Advantages of Squirrel Cage Induction Motors
- Squirrel cage induction motor are cheap and it’s also got simple construction
- Compare with other motors this motor got rugged in construction.
- The maintenance cost for squirrel cage induction motor are quite low.
- The starting arrangement of squirrel cage induction motors is simple.
- This type of motor got high overload capacity and high power factor.
- This motor got more pull out torque and this got great maximum power output.
Disadvantages of Squirrel Cage Induction Motor
- IT got poor starting torque due to the low resistance in the rotor.
- Speed regulation of squirrel cage induction motor is not possible.
- At light load, the power factor is very low.
- It’s very sensitive to change in supply voltage.
Applications of Squirrel Cage Induction Motors
Squirrel cage induction motor drives for can use for following applications such as.
- Flour Mills
- Printing Machine
- Shaft drive which uses small power.