Exam Question
Differentiate between squirrel cage and wound rotor motors, of the three phase a.c. induction type, with respect of the following: (16)
(a) Rotor construction
(b) Torque characteristics
(c) Speed varintion.
Class 4 (4th Engineer)
MET
📅 Aug 2024
Reference Answer
### Introduction
Three-phase A.C. induction motors operate on the principle of a rotating magnetic field (RMF) generated by the stator windings. This RMF induces a current in the rotor conductors, which in turn creates a magnetic field. The interaction between the stator's RMF and the rotor's magnetic field produces torque, causing the rotor to turn in the same direction as the RMF, but at a slightly lower speed (this speed difference is known as 'slip'). The primary distinction between the two main types of induction motors—Squirrel Cage and Wound Rotor (or Slip-Ring)—lies in the physical and electrical construction of the rotor. This fundamental difference dictates their torque characteristics, starting performance, speed control capabilities, cost, and applications.
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### (a) Rotor Construction
Three-phase A.C. induction motors operate on the principle of a rotating magnetic field (RMF) generated by the stator windings. This RMF induces a current in the rotor conductors, which in turn creates a magnetic field. The interaction between the stator's RMF and the rotor's magnetic field produces torque, causing the rotor to turn in the same direction as the RMF, but at a slightly lower speed (this speed difference is known as 'slip'). The primary distinction between the two main types of induction motors—Squirrel Cage and Wound Rotor (or Slip-Ring)—lies in the physical and electrical construction of the rotor. This fundamental difference dictates their torque characteristics, starting performance, speed control capabilities, cost, and applications.
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### (a) Rotor Construction
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