The excitation system of the alternator is a critical component responsible for supplying the necessary field current to the generator’s rotor winding. This field current creates a magnetic field, inducing voltage in the stator windings, thus producing electrical power.
The excitation system plays a vital role in regulating the output voltage, controlling reactive power, and ensuring the stable and efficient operation of the alternator.
Importance of the Excitation System of Alternator: The excitation system is a crucial part of an alternator, ensuring that it operates within the desired voltage and frequency range. It is responsible for maintaining the generator’s terminal voltage under varying load conditions, keeping it synchronized with the grid, and supporting reactive power flow.
Components Of The Excitation System Of Alternator:
The key components of the excitation system include:
Exciter: The exciter is a small DC generator, mounted on the same shaft as the main alternator rotor. It generates the initial field current required for the alternator’s rotor winding.
Voltage Regulator: The voltage regulator is a control unit that monitors the alternator’s output voltage and adjusts the exciter’s field current to maintain a constant terminal voltage.
Automatic Voltage Regulator (AVR): In modern alternators, the voltage regulator is often integrated with the exciter, forming the Automatic Voltage Regulator (AVR). The AVR performs the voltage regulation function more precisely and efficiently.
Brushes and Slip Rings: These components provide the electrical connection between the rotating exciter and the stationary AVR or voltage regulator.
Self-Excitation And Separate Excitation Systems
There are two main types of excitation systems used in alternators:
Self-Excitation System: In a self-excited alternator, the exciter generates the field current using a small residual magnetic flux present in the rotor core during startup. Once the alternator starts producing power, it generates its field current, and the excitation system of the alternator becomes self-sustaining.
Separate Excitation System: In a separate excitation system, the exciter is powered by an external DC source, such as a battery or a separate generator. This system offers better control over the field current and is commonly used in large alternators and power plants.
Read More : Alternator Excitation System
