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the generator construction is divided to Stator and Rotor (Connected to the Drive Motor ) , To produce Electricity ( voltage Across the Stator terminals ) the theory Follows the Magnetic Phenomena ( LH Rule ) , DC Current ( One Direction ) Flow through the Rotor Winding Produce the Magnetic Field with Magnitude and Frequency Related to the speed of the drive motor cuts the stator winding produce EMF with the same frequency.
Excitation Current which Flows through the rotor winding which produce the Rotor magnetic Field has different means of production As Static excitation , DC Exciter and brush-less Exciter
DC Exciter is small Generator coupled to the Rotor shaft feed current through slip rings to the main rotor winding to produce constant Voltage and exciter output controlled by varying the field current of the exciter
Static Exciter DC Current for the Rotor Winding is drived from the generator output by utlizing power electronics to convert the AC to Controlled DC and feed to the rotor through slip rings . this method advantage is less mechanical load but it needs a battery bank during startup while no output from the generator
Brush-less Exciter the exciter armature is on the same shaft the output of the armature is rectified using Rotating Diodes then feed to the main rotor winding , controlling the stator exciter current vary the output from the armature then varying the output to the main rotor winding this controlled is handled using the automatic voltage regulator (AVR ) PCB which feed the generator voltage output and according sensing that output start varying the field current according to parameters like Voltage Droop.
each excitation method has its advantage and disadvantage but the most common method which is the brush-less exciter excitation method which control the output due to the load on the generator or generator by utizing AVR PCB which can communicate which each other in sharing mode.
Generating Bus voltage control, Reactive power control and Transient Stability of Power Plant depends on it
To produce electrical voltage (E) from electrical generator needs : magnetic field (B), Conductor (L) and velocity (movement) between conductor and magnetic field (V). E=LBV
Excitation system is combination of electronic circuit and electrical circuit to produce magnetic field from DC voltage.
