Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
48 views
in General by (108k points)
closed by

Directions: It consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II). Examine these two statements carefully and select the answer using the codes given below:

Statement (I): In a dc shunt generator the ‘build-up’ induced voltage, at its terminals, is given by the intersection point of the Field Resistance Line (FRL) with the No-Load Characteristics (NLC) of the machine.

Statement (II): The generator fails to build up any voltage at its terminals, when the slope of the FRL is higher than that of the straight line portion of the NLC.


1. Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
2. Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)
3. Statement (I) is true but Statement (II) is false
4. Statement (I) is false but Statement (II) is true

1 Answer

0 votes
by (101k points)
selected by
 
Best answer
Correct Answer - Option 1 : Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)

Characteristics of a shunt generator:

  • Field coil (F1, F2) along with a series external resistance is connected in parallel with the armature terminals (A1, A2) of the machine as shown in figure.
  • Suppose there exists some residual field. Therefore, if the generator is driven at rated speed, we should expect a small voltage to be induced across the armature.
  • But this small voltage will be directly applied across the field circuit since it is connected in parallel with the armature.
  • Hence a small field current flows producing additional flux. If it so happens that this additional flux aids the already existing residual flux, total flux now becomes more generating more voltage.
  • This more voltage will drive more field current generating more voltage. Both field current and armature generated voltage grow cumulatively.
  • This growth of voltage and the final value to which it will settle down can be understood by referring to the figure given where two plots have been shown.
  • One corresponds to the O.C.C at rated speed and the other one is the V-I characteristic of the field circuit which is a straight line passing through origin and its slope represents the total field circuit resistance.

 

 

  • Initially voltage induced due to residual flux is obtained from O.C.C and given by Od.
  • The field current thus produced can be obtained from field circuit resistance line and given by Op.
  • In this way voltage build up process continues along the staircase. The final stable operating point (M) will be the point of intersection between the O.C.C and the field resistance line.
  • If field circuit resistance is increased, final voltage decreases as point of intersection shifts toward left.
  • The field circuit resistance line which is tangential to the O.C.C is called the critical field resistance.
  • If the field circuit resistance is more than the critical value, the machine will fail to excite, and no voltage will be induced.

 

Therefore, both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I).

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...