The effect of armature reaction in a DC machine is that it both weakens the main field flux and distorts its distribution. Here’s a breakdown of the effects:
Weakening of main field flux: The armature current in a DC machine creates a magnetic field that opposes the main field flux produced by the field winding. This opposition weakens the overall main field flux within the machine.
Distortion of main field flux: The armature current also generates a magnetic field that interacts with the main field flux, causing a distortion in its distribution. This distortion is mainly due to the magnetic field produced by the armature current being at right angles to the main field flux.
These combined effects of armature reaction can have several consequences on the performance of a DC machine, including:
Reduction in the overall flux density and magnetic field strength in the machine.
Shifting of the neutral plane, where the commutation process occurs, leading to potential commutation issues.
Uneven distribution of magnetic flux in the air gap, resulting in uneven torque production and increased losses.
Therefore, the correct answer is option C: “Both B and C.” Armature reaction weakens the main field flux and distorts its distribution within the DC machine.