The power factor of an alternator depends on the type of load.
The power factor is a measure of the efficiency of the energy transfer from the generator to the load. It is defined as the ratio of the real power (also called active power) delivered to the load to the apparent power delivered to the load.
For resistive loads, such as incandescent bulbs or electric heaters, the power factor is unity (i.e., 1). This is because the current through a resistive load is in phase with the voltage across it, and there is no reactive power component.
For inductive loads, such as electric motors or transformers, the power factor is typically less than unity, because the current through an inductive load lags the voltage across it, leading to a reactive power component that does not contribute to useful work.
For capacitive loads, such as capacitor banks or some types of power electronics, the power factor can be greater than unity, because the current through a capacitive load leads the voltage across it, leading to a reactive power component that can cancel out reactive power from other loads.
Therefore, the power factor of an alternator depends on the type of load that is connected to its output terminals, and the generator's voltage regulation and excitation control systems are designed to maintain a high power factor under varying load conditions.