Exam Question
With reference to a 3-speed A.C Cage motor driven cargo winch:
(a) Sketch a circuit diagram for a pole change motor (8)
(b) Describe how speed change and braking are achieved (8)
Class 4 (4th Engineer)
MET
📅 Dec 2022
Reference Answer
### (a) Pole Change Motor Circuit Diagram
A 3-speed pole changing squirrel cage induction motor achieves different speeds by altering the number of active magnetic poles in the stator. This is typically accomplished using two independent stator windings housed in the same slots, or a single special winding (like a Dahlander connection for a 2:1 speed ratio) paired with a separate winding for the third speed.
**Key Components in the Circuit Diagram:**
1. **Main Supply:** A three-phase AC supply (L1, L2, L3) protected by fuses or a circuit breaker.
A 3-speed pole changing squirrel cage induction motor achieves different speeds by altering the number of active magnetic poles in the stator. This is typically accomplished using two independent stator windings housed in the same slots, or a single special winding (like a Dahlander connection for a 2:1 speed ratio) paired with a separate winding for the third speed.
**Key Components in the Circuit Diagram:**
1. **Main Supply:** A three-phase AC supply (L1, L2, L3) protected by fuses or a circuit breaker.
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