Interpoles in dc machines ___

Electrical Engineering MCQ Electrical Machines MCQ
1

Consider the following statements :

Interpoles in dc machines

  1. reduce armature reaction effects in the interpolar region
  2. have the same dimension as main polls
  3. have their windings connected in series with the armature
  4. have same number of turns as the armature
  5. have the polarity same as that of the main pole ahead in a motor From these,

the correct statements are

A. 1, 2 and 3
B. 1, 3 and 5
C. 1, 2, 3 and 5
D. 1 and 3

Show Answer

Answer: D

Share your understanding of this question with the correct explanation.

2

The correct answer is D. The statements 1 and 3 are correct.

Explanation:

  1. Interpoles in DC machines reduce armature reaction effects in the interpolar region: This statement is correct. Interpoles are designed to counteract the armature reaction in the interpolar region of a DC machine. They produce a magnetic field that opposes the armature field and helps in reducing the armature reaction effects, particularly the cross-magnetizing effect, in that specific region.
  2. Interpoles have the same dimension as main poles: This statement is incorrect. Interpoles are smaller in size compared to the main poles. They are typically narrower and shorter in order to fit in between the main poles and provide the necessary magnetic field for commutation.
  3. Interpoles have their windings connected in series with the armature: This statement is correct. The windings of the interpoles are connected in series with the armature windings. This allows the interpoles to produce the required flux for commutation in coordination with the armature current.
  4. Interpoles have the same number of turns as the armature: This statement is incorrect. Interpoles usually have a smaller number of turns compared to the armature. The number of turns is chosen to achieve the desired magnetic field strength and commutation performance.
  5. Interpoles have the polarity same as that of the main pole ahead in a motor: This statement is incorrect. The polarity of the interpoles is opposite to that of the main poles in advance. This is necessary to aid in the commutation process. The opposite polarity of the interpoles creates a magnetic field that opposes the armature field in the region of commutation, helping to facilitate the reversal of current in the armature coils.

Therefore, the correct answer is D, as statements 1 and 3 are correct.