exciteeraus

Exciteeraus (excitation) refers to the process of energizing the field winding of an electrical machine to create a magnetic field. In synchronous machines, the excitation current establishes the rotor flux that interacts with the stator field to generate voltage and torque. The term is widely used in Finnish engineering literature and textbooks.

In generators, the magnitude of the field current controls the level of the generated voltage. Increasing excitation increases the rotor flux and the output voltage up to magnetic saturation; conversely, reducing excitation lowers voltage. An automatic voltage regulator (AVR) continuously adjusts the excitation to maintain a chosen terminal voltage under changing load.

Excitation methods include separate excitation, self-excitation, and brushless excitation. Separate excitation uses an independent DC source for the field winding. Self-excitation relies on the machine’s own output, often via rectifiers, to supply the field current. Brushless excitation employs rotating rectifiers or an external exciter to feed the field windings without direct brush contact.

In practice, excitation is essential for starting and maintaining operation in synchronous machines. It determines the available reactive power, voltage regulation, and transient stability. Proper control of excitation helps manage power system dynamics, including voltage support during faults and recovery after disturbances. In DC machines, excitation similarly controls flux and performance.

See also: Excitation, Synchronous generator, Automatic voltage regulator, Field winding.