The exciter is an electrical device that supplies direct current to the field winding of the generator, at the required voltage level to overcome the resistance of the winding.
The term exciter is very often used in the field of electrical machines and power generation.
An exciter is usually a small generator that supplies the magnetic field for the main generator. The exciter is generally mounted on the same shaft as the main generator. The main function of an exciter is to provide the necessary field current to the rotor winding of the main generator, which in turn produces the desired output voltage. The exciter is usually a small direct-current (DC) generator that produces a controlled output voltage, typically between 100 and 300 volts.
An AC generator utilizes a magnetic field that rotates in the rotor to induce a voltage in the stator windings. While a permanent magnet can be used for this purpose, it provides a fixed voltage output that cannot be adjusted. On the other hand, a rotating coil can generate a rotating magnetic field that can be regulated to control the strength of the field and the resulting voltage output. This regulation is achieved by the exciter, which controls the variable current fed into the rotor windings.
In the case of larger generators and motors, brushless exciters are very often employed to supply the DC field current to the machine.
A brushless exciter is a compact ac generator whose field circuit is mounted on the stator and its armature circuit mounted on the rotor shaft.
Here a three-phase rectifier circuit is used for converting the three-phase output of the exciter generator to direct current. The rectifier circuit is also mounted on the shaft of the generator and is then fed into the main dc field circuit.
The excitation system is a critical component of a generator, as it determines the stability, reliability, and overall performance of the generator. Proper excitation ensures that the generator produces a steady and accurate output voltage, which is essential for the operation of the electrical power system.