Machine types – What does “squirrel-cage” describe? Statement: “The term squirrel-cage applies to a type of three-phase AC generator.” Choose the best answer.
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ATrue
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BFalse
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CTrue only for permanent-magnet alternators
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DTrue for single-phase machines only
Answer
Correct Answer: False
Explanation
Introduction / Context:Machine nomenclature can be confusing across motors and generators. “Squirrel-cage” is a widely used term in industry and examinations. Correctly identifying where it applies helps avoid misinterpretations in specifications and maintenance manuals.
Given Data / Assumptions:
- Standard AC machines: induction motors, synchronous machines, and alternators.
- “Squirrel-cage” refers to a specific rotor construction.
- Focus on whether it describes a generator type.
Concept / Approach:
“Squirrel-cage” describes the rotor of an induction motor: aluminum or copper bars shorted at both ends by end rings, resembling a cage. It is not a descriptor for alternators (AC generators). Alternators typically have a wound or permanent-magnet rotor and a three-phase stator; the term “squirrel-cage generator” is not standard terminology.
Step-by-Step Solution:
Identify that induction machines are predominantly motors with cage rotors.Alternators (synchronous generators) use DC-excited or PM rotors, not cage rotors as a classification.Therefore, the statement is false.Verification / Alternative check:
Catalogs and datasheets label “squirrel-cage induction motors,” while generators are labeled “alternators” or “synchronous generators,” confirming standard usage.
Why Other Options Are Wrong:
Qualifiers about permanent magnets or single-phase do not transform the term into a generator descriptor.
Common Pitfalls:
Assuming any rotating electrical machine could be termed “squirrel-cage.” Keep the association strictly with induction motor rotor construction.
Final Answer:
False.