Variation in dc excitation of a synchronous motor causes variation in

Question

Question

This question was previously asked in

UKPSC JE Electrical 2013 Official Paper II (Held on 7 Nov 2015)

Answer 1

The correct answer is 'option 2'

Concept:

The variation due to dc excitation can be understood from the V and inverted V curves.

SSC JE Electrical 52 17Q Jan 27 Second Shift Machines Hindi images Q14

The above graph is of inverted V curve, showing variation in pf due to dc excitation.

F1 Raviranjan 17-2-22 Savita D8

The above graph is of V curve showing variation in armature current due to dc excitation.

Solution:

Variation in dc excitation thus results in the variation of both power factor and armature current.