When a pure inductive load is connected to the alternator, what is the effect of armature reaction?

Armature Reaction in Synchronous Machines:

Armature reaction refers to the impact of the magnetic field generated by the armature (stator) current on the distribution of the main magnetic field created by the rotor. This interaction can alter the effective magnetic field within the machine, affecting its performance.

Types of Armature Reaction:

• Magnetizing (or Strengthening) Armature Reaction: This occurs when the armature field aids the main field, thus strengthening the resultant magnetic field. This is typically seen when the machine is under an inductive load.
• Demagnetizing (or Weakening) Armature Reaction: This happens when the armature field opposes the main field, thereby weakening the resultant magnetic field. This is commonly observed under a purely inductive load.
• Cross Magnetization: This occurs when the armature field is perpendicular to the main field, leading to distortion of the resultant magnetic field without necessarily strengthening or weakening it. This typically happens under a purely resistive load.

Effect of Armature Reaction with Pure Inductive Load:

• When a pure inductive load is connected to an alternator, the current lags the voltage by 90 degrees.
• In this case, the armature reaction primarily produces a demagnetizing effect because the armature field opposes the main field created by the rotor.
• As a result, the resultant magnetic field is weakened, reducing the overall flux in the machine.
• This demagnetizing effect can lead to a reduction in the terminal voltage of the alternator.

Therefore, when a pure inductive load is connected to the alternator, the effect of armature reaction is Demagnetization.