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SarkariResultOutBMS · 2024

Previous Year Question

Consider the following statements: EMF induced per phase in an alternator depends on 1. Frequency 2. Number of turns per phase 3. Pitch factor 4. Distribution factor Select the correct option:
  1. 1 and 2 only
  2. 2 and 3 only
  3. 1, 2, 3 and 4
  4. 1, 2 and 3 only

Correct answer: C

Explanation

The generated RMS emf per phase is E=4.44 kp kd f Φ T. It therefore depends on frequency, turns per phase, pitch factor and distribution factor (and flux per pole). All four listed factors affect the induced emf, so option C.

Formula

Ephase=4.44 kp kd f Φ T

Step-by-step solution

Factors Affecting Alternator EMF explanatory diagram

Correct Answer

C — 1, 2, 3 and 4

Concept and Reasoning

The generated RMS emf per phase is E=4.44 kp kd f Φ T. It therefore depends on frequency, turns per phase, pitch factor and distribution factor (and flux per pole). All four listed factors affect the induced emf, so option C.

Calculation / Key Relation

Ephase=4.44 kp kd f Φ T

Exam Takeaway

Alternator emf equation directly lists the relevant winding and frequency factors.

Common Mistake

Do not omit winding factors kp or kd when the winding is short-pitched/distributed.

Common mistake

Do not omit winding factors kp or kd when the winding is short-pitched/distributed.

Exam tip

Alternator emf equation directly lists the relevant winding and frequency factors.

Quick method

Alternator emf equation directly lists the relevant winding and frequency factors.