Correct Answer - Option 3 : armature resistance, leakage reactance and armature reactance
The main reasons for voltage drop in the alternator are:
1. Armature resistance: The voltage drop caused by armature resistance per phase is IRa
Where I is the phase current in ampere and Ra is armature resistance in ohm.
Additional energy loss such as Hysteresis loss, Eddy current Loss, and loss due to unequal distribution of currents are part of armature resistance losses.
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 EMF is generated. This effect produces armature reactance that is equal to 2πfl.
This armature reactance is called leakage reactance XL and this leakage flux is proportional to the armature current.
3. Armature reaction: When the load current flows in the stator conductor, it produces a magnetic field which 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 armature reaction. The armature reaction depends upon the power factor of the load.
4. Synchronous reactance: The combination of leakage reactance along with armature reaction is called as synchronous reactance.
