Changing in the excitation in grid having an alternator connected to it will having the following effect:
A. Change in active component of load
B. Change in reactive component of load
C. Change in Power Factor of Load
D. The frequency of the generated wave form will be affected
E. B and C (correct)
The correct answer and explanation is:
The correct answer is E. B and C.
Explanation:
In an alternator connected to a grid, excitation refers to the process of supplying the alternator with a DC current in order to generate the magnetic field necessary for its operation. Changing the excitation of the alternator will affect its output in terms of both reactive power and power factor, but it will not directly affect the frequency of the generated waveform or the active component of the load.
- Change in Reactive Component of Load (B): The excitation of the alternator directly influences the reactive power it generates. Reactive power is responsible for maintaining the voltage levels in the system and is primarily associated with inductive and capacitive loads. When the excitation increases, the alternator produces more reactive power, which increases the reactive component of the load. Conversely, reducing the excitation will decrease the reactive power output.
- Change in Power Factor of Load (C): Power factor is the ratio of real power (active power) to apparent power in the system. A change in excitation can affect the reactive power output, and since power factor is dependent on both active and reactive power, adjusting the excitation can lead to a change in the power factor of the load. If more reactive power is supplied (by increasing excitation), the system’s power factor may decrease (more inductive). If the excitation is reduced, the power factor may improve (less inductive).
- Why Not A and D?
- Active Component of Load (A): Changing the excitation of an alternator does not directly impact the active power (real power), which is related to the mechanical power input and the efficiency of the generator, not the excitation.
- Frequency of the Generated Waveform (D): The frequency of the generated waveform in an alternator is primarily determined by the rotational speed of the alternator’s rotor and the number of poles, not by the excitation. Therefore, changing the excitation will not affect the frequency of the generated waveform.
Thus, altering the excitation of an alternator affects the reactive power and the power factor of the load, making option E the correct choice.