Which of the following statements accurately describes voltage drop due to armature leakage reactance in an alternator on load?

The correct answer is option 4.

The main reasons for the voltage drop in the alternator are:

1.) Armature resistance

The voltage drop caused by armature resistance per phase is IR_a, which is in phase with armature current I.

Additional energy loss such as Hysteresis loss, Eddy current Loss, and loss due to unequal distribution of currents are part of armature resistance losses. However, these losses are practically negligible.

2.) Armature leakage reactance

When the load current flows through the armature winding it builds up the local flux which cuts the winding and counters the EMF generated. This effect produces armature reactance that is equal to 2πfl.

This armature reactance is called leakage reactance X_L and this leakage flux is proportional to the armature current. Therefore, the voltage drop due to armature leakage reactance increases with increasing load.

3.) Armature Reaction

When the load current flows in the stator conductor, it produces a magnetic field that has a cross-magnetization, de-magnetization, and magnetizing effect upon the main flux due to the field winding.

Such an effect of armature current upon the main flux is known as an armature reaction. The armature reaction depends upon the power factor of the load.

4.) Synchronous Reactance

The combination of leakage reactance along armature reaction is called synchronous reactance.