Reactive Power in AC Generators

Reactive power is the imaginary power.

It is the power that gets usually exchanged between the capacitive and inductive elements of the circuit.

Assuming no resistive loss anywhere, there is no significance of this power, except that the Generator has to compensate by acting as a virtual capacitor or inductor as the case may be (this is done by the field current control)

this is the basis.

Details could be given, but what is said above is enough to start the chain of thoughts in correct direction (hopefully).

however it has a smell of homework and somehow a large number of questions of this types from guests are that .

Guest,

The engine driving a generator has a fuel consumption dependent on the output power at its shaft. This power ( torque x speed) will be applied to the shaft of the generator (as input power) (kW). As output power for the generator is the active power (load) component (kW) + losses (mechanical and electrical). The active power generated is the same for the same active/real load, but, since the currents in the connecting wires are dependent on the apparent power (kVA), the losses at a lower power factor (considering the active power contant, thus the apparent power higher) are going to be higher.

In addition, if excitation power comes from the same generator output (auto-excitation), the excitation power is higher at a lower power factor (inductive), while lower at a lower power factor (capacitive) - In this case the aspects have to be considered separately (inductive (lagging) - capacitive (leading).

So, a generator that delivers power at a lower power factor (more reactive power for inductive load) will use more fuel . Best results are when generating at power factor 1.