What are the factors that cause a change of alternator terminal voltage when it is loaded?

The alternator terminal voltage can change when loaded due to several factors, including voltage drop caused by the internal impedance of the alternator, which consists of resistance and reactance. As the load increases, the current draw rises, leading to increased voltage drop across the alternator's internal components. Additionally, the saturation of the magnetic core can occur as the load increases, further affecting the output voltage. Finally, variations in engine speed and excitation levels can also influence terminal voltage under load conditions.