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Number of slip rings in squirrel cage induction motor is
Zero
One
Two
Three
Zero
A squirrel cage induction motor uses a rotor constructed with short-circuited copper or aluminum bars, eliminating the need for external electrical connections to the rotating part. Consequently, it requires no slip rings or brushes, making the design robust and maintenance-free.
A squirrel cage induction motor uses a rotor constructed with short-circuited copper or aluminum bars, eliminating the need for external electrical connections to the rotating part. Consequently, it requires no slip rings or brushes, making the design robust and maintenance-free.
s=NsтАЛNsтАЛтИТNrтАЛтАЛ тАФ Slip calculation formula
In an induction motor, the stator creates a rotating magnetic field that induces current in the rotor bars via electromagnetic induction. In the squirrel cage design, these bars are permanently short-circuited at both ends by conducting end rings. Since the circuit is permanently closed, there is no requirement for external resistances or slip rings to connect the rotor windings to the external circuit.
Squirrel cage motors are characterized by their simple, rugged construction.
Slip rings are exclusively used in Wound Rotor (Slip Ring) Induction Motors to add external resistance for speed control or starting torque improvement.
The absence of brushes and slip rings reduces friction and sparking, increasing motor lifespan.
Extremely robust and reliable construction
Lower maintenance cost due to lack of brushes
High efficiency and lower cost compared to slip ring motors
Poor starting torque characteristics
Cannot use external resistance for speed control
High starting current compared to slip ring motors
Industrial fans and blowers
Centrifugal pumps
Machine tools
Conveyor belts
| Feature | Squirrel Cage Motor | Wound Rotor (Slip Ring) Motor |
|---|---|---|
Slip Rings | Zero | Three |
Slip ring motors typically have three slip rings for a 3-phase connection.
Option D represents a Slip Ring Induction Motor rotor, not a Squirrel Cage one.
A is correct тАФ A squirrel cage induction motor has a permanently short-circuited rotor, requiring zero slip rings.
Remember: If a motor requires external rotor resistance (for soft starting or speed control), it must be a slip-ring motor; if it is 'squirrel cage', it is inherently a fixed-resistance rotor machine.