Important Electrical Machine Design Multiple Choice Questions and Answers

26.  In turbo alternators the rotor diameter is it limited to about 1.2 m due to

   A. Centrifugal forces

   B. Deflection

   C. Critical speed

   D. All of the above

27.  The starter core of turbo-alternators is made of

   A. Segmental limitations of low loss silicon steel

   B. Cold rolled non-oriented steel with about 3% silicon

   C. Cold rolled grain oriented steel with about 4% silicon

   D. Both A and B

28.  Multiple inlet system of air cooling of turbo alternators can be employed for machines of rating up to

   A. 20 MW

   B. 100 MW

   C. 60 MW

   D. 250 MW

29.  Damper winding is used to

   A. Reduce air gap harmonic flux

   B. Reduce oscillations

   C. Increase stability limits

   D. Resist the moisture

30.  Usual values of ac recommended for silent pole machines are

   A. 5000 to 10,000 ampere-conductors/m

   B. 10,000 to 20,000 ampere-conductors/m

   C. 20,000 to 50,000 ampere-conductors/m

   D. 50,000 to 100000 ampere-conductors/m

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