The correct answer is: A. Is always present
Armature reaction is the magnetic field produced by the current flowing through the armature windings of a generator. It is always present, regardless of whether the generator is supplying rated load or not.
Armature reaction can have a significant effect on the performance of a generator. It can cause a decrease in the terminal voltage of the generator, and it can also cause a decrease in the power factor of the generator.
To minimize the effects of armature reaction, generators are often designed with a compensating winding. The compensating winding is placed in the stator of the generator, and it is designed to produce a magnetic field that opposes the armature reaction field. This helps to keep the terminal voltage and power factor of the generator more constant.
Here is a brief explanation of each option:
- Option A: Is always present. This is the correct answer. Armature reaction is always present, regardless of whether the generator is supplying rated load or not.
- Option B: Is always absent. This is incorrect. Armature reaction is always present.
- Option C: May be sometimes present. This is incorrect. Armature reaction is always present.
- Option D: None of the above. This is incorrect. The correct answer is A.