Question
Download Solution PDFIn a 3-phase alternator, weakening of the main flux due to armature reaction results in:
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFThe correct answer is option 2.
Armature Reaction in Alternator
In an alternator, armature reaction refers to the effect of the armature current on the magnetic field of the machine. This interaction results in a distortion of the magnetic field, leading to changes in the terminal voltage
Effect of Load Power Factor on Armature Reaction
- Unity Power Factor Load: When the load has a unity power factor, i.e., a pure resistive load, then the armature reaction distorts the main field flux in the air gap of the machine and does not weaken it.
- Zero Lagging Power Factor Load: When the load power factor is zero lagging i.e. pure inductive load, then the armature reaction weakens the main field flux. Due to the reduction in the main field flux, the generated EMF is decreased.
- Zero Leading Power Factor Load: When the load power factor is zero leading, i.e. pure capacitive load, then the armature reaction strengthens the main field flux. This causes an increase in the generated voltage.
Nature of armature reaction on alternator:
|
Power factor |
Nature |
|
Unity |
Cross-magnetizing |
|
Zero PF lagging |
Purely demagnetizing |
|
Zero PF leading |
Purely magnetizing |
|
0.8 lagging |
Partially cross-magnetising and partially demagnetizing |
|
0.8 leading |
Partially cross magnetizing and partially magnetizing |
Last updated on May 29, 2025
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