Electrical Machine Design(Engineering > Electrical Engineering ) Questions and Answers

Question 1. Commercial available medium size machines have a speed range of ______ .
  1.    200 to 400 r.p.m.
  2.    600 to 1000 r.p.m.
  3.    1000 to 1500 r.p.m.
  4.    2000 to 2500 r.p.m.
Explanation:-
Answer: Option D. -> 2000 to 2500 r.p.m.
Question 2. The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are
  1.    0.5 to 0.8 Wb/m²
  2.    0.8 to 1.0 Wb/m²
  3.    1.1 to 1.35 Wb/m²
  4.    1.4 to 1.8 Wb/m²
Explanation:-
Answer: Option C. -> 1.1 to 1.35 Wb/m²
Question 3. The electrical power to a meggar is provided by
  1.    battery
  2.    permanent magnet D.C. generator
  3.    A.C. generator
  4.    any of the above
Explanation:-
Answer: Option B. -> permanent magnet D.C. generator
Question 4. Various adjustments in an energy meter include
  1.    light load or friction
  2.    lag and creep
  3.    overload and voltage compensation
  4.    temperature compensation
  5.    all of the above
Explanation:-
Answer: Option E. -> all of the above
Question 5. In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made
  1.    equal to that of armature mmf
  2.    less in comparison with the armature mmf
  3.    large in comparison with the armature mmf
  4.    none of the above
Explanation:-
Answer: Option C. -> large in comparison with the armature mmf
Question 6. For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used?
  1.    1.0 to 1.2 A/mm²
  2.    1.5 to 2.0 A/mm²
  3.    2.2 to 3.2 A/mm²
  4.    3.2 to 4.2 A/mm²
Explanation:-
Answer: Option C. -> 2.2 to 3.2 A/mm²
Question 7. Instrument transformers are
  1.    potential transformers
  2.    current transformers
  3.    both (A) and (B)
  4.    power transformers
Explanation:-
Answer: Option C. -> both (A) and (B)
Question 8. The rectifier instrument is not free from
  1.    temperature error
  2.    wave shape error
  3.    frequency error
  4.    all of the above
Explanation:-
Answer: Option C. -> frequency error
Question 9. In order to achieve high accuracy, the slide wire of a potentiometer should be
  1.    as long as possible
  2.    as short as possible
  3.    neither too small not too large
  4.    very thick
Explanation:-
Answer: Option A. -> as long as possible
Question 10. In D.C. machines the number of slots per pole usually lies
  1.    between 2 to 4
  2.    between 6 to 8
  3.    between 9 to 16
  4.    between 20 to 30
Explanation:-
Answer: Option C. -> between 9 to 16
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