Synchronous Generator MCQ Part 8

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Synchronous generator MCQ Part 8

The power factor of individual alternator operating along other alternators

When a number of alternators are operating in parallel, the power factor at which each alternator operated depends on:

  1. Driving torque provided by prime mover
  2. Field excitation
  3. Power factor of load
  4. All of the above

Correct answer: 2. Field excitation

Turbo alternators have rotors that have

Turbo alternators have rotors that have:

  1. Small diameter and long axial length
  2. Small diameter and small axial length
  3. Large diameter and long axial length
  4. Large diameter and long axial length

Correct answer: 1. Small diameter and long axial length

Turbo alternators usually have two poles that turn at high speed (3000 in case of 50 Hz frequency). It is a design requirement to make a smaller diameter. For a given volume of the machine if the diameter is low the length needs to be longer. This makes turbo alternator to have a small diameter and longer axial length.

Turbo alternators are normally designed with how many poles

Turbo alternators are normally designed with how many poles:

  1. Two
  2. Four
  3. Six
  4. Eight

Correct answer: 1. Two

For generating 60 Hz power in a two pole machine, the rotor should turn at

For generating 60 Hz power in a two pole machine, the rotor should turn at:

  1. 900 RPM
  2. 1800 RPM
  3. 3600 RPM
  4. 7200 RPM

Correct answer: 3. 3600 RPM

Explanation: η = (120 * f)/P = (120 * 60)/2 = 3600 RPM

For two or four number of poles the which type of rotor construction is preferred

For two or four number of poles the which type of rotor construction is preferred:

  1. Salient type
  2. Non-salient type

Correct answer: 2. Non-salient

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