Exam Question
(a) What is the function of slip rings in an AC motor? (6)
(b) Compare Direct-On-Line (DOL), Star-Delta, and Auto-Transformer methods of motor starting. Which method is preferred and why? (10)
Class 4 (4th Engineer)
MET
📅 Nov 2025
Reference Answer
### (a) Function of Slip Rings in an AC Motor
Slip rings are exclusively found in **wound rotor induction motors**, also known as slip-ring motors. They are not present in the more common squirrel cage induction motors. Their primary function is to provide an electrical connection between the rotating rotor windings and the stationary external control circuitry.
This connection serves two main purposes:
1. **Starting Performance Modification:**
Slip rings are exclusively found in **wound rotor induction motors**, also known as slip-ring motors. They are not present in the more common squirrel cage induction motors. Their primary function is to provide an electrical connection between the rotating rotor windings and the stationary external control circuitry.
This connection serves two main purposes:
1. **Starting Performance Modification:**
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