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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Which part is not available in squirrel cage induction motor ?
Frame
Stator
Rotor
Slip ring
Slip ring
A squirrel cage induction motor is named for its rotor, which consists of uninsulated metal bars short-circuited at both ends by end rings. Since the rotor circuit is permanently short-circuited within the rotor structure itself, it does not require slip rings or external resistance connections.
A squirrel cage induction motor is named for its rotor, which consists of uninsulated metal bars short-circuited at both ends by end rings. Since the rotor circuit is permanently short-circuited within the rotor structure itself, it does not require slip rings or external resistance connections.
s=nsns−nr — slip of the induction motor
Te∝ΦI2cosϕ2 — electromagnetic torque production
The stator produces a rotating magnetic field that induces EMF in the rotor bars via electromagnetic induction. Due to the short-circuited nature of the cage, a large current flows through the bars, interacting with the magnetic field to produce torque. Unlike slip-ring motors, there is no physical connection to external circuitry, making the design robust and maintenance-free.
The rotor bars are skewed to reduce magnetic hum and cogging.
Squirrel cage motors have high starting current and low starting torque compared to wound rotor types.
Maintenance is minimal as there are no brushes or slip rings to wear out.
Simple and rugged construction
Lower cost and maintenance
High operational efficiency
Low starting torque
High starting current
Speed control is difficult
Industrial fans and blowers
Centrifugal pumps
Small machine tools
| Feature | Squirrel Cage | Slip Ring |
|---|---|---|
Construction | Permanent short-circuit | Winding connected to rings |
Slip rings are exclusive to Wound Rotor Induction Motors (WRIM) to allow for the insertion of external resistance for speed control or starting torque improvement.
Option A (Frame), B (Stator), and C (Rotor) are essential mechanical or electromagnetic components present in all standard induction motors.
D is correct — Squirrel cage induction motors do not use slip rings as the rotor bars are permanently short-circuited by end rings.
Always remember that 'Squirrel Cage' implies a maintenance-free, fixed-resistance rotor, whereas 'Slip Ring' (Wound Rotor) allows external control.