It is well known to use direct current synchronous generator excitation. In the past, he was excited synchronous generator, the DC current is supplied attached to the DC exciter. Armature rotating DC exciter alternator belt is a mechanical commutator. It closed its multiphase armature windings cutting the stator magnetic field generated polyphase alternating current, due to the rectification of mechanical commutator and brushes composed of rectification system on the brush to get a DC, and then through another set of brushes, slider DC system will get delivered to the rotor field winding synchronous generator de-excitation, and therefore in principle on the commutator DC exciter is a rectifier, apparently can replace pipe section with a set of silicon dioxide, and the development of power semiconductor devices provided this condition. The axis of the semiconductor element and the rotation of the generator consolidation together, you can cancel the commutator sliding contact portion, sliders, etc., use a diode into a direct current. DC to the rotor excitation winding excitation. This is the brushless system.

Here we have a typical several different excitation system, introduce it works.

First, the principle of phase compound excitation

By the linear reactors DK armature winding tap voltage shift Meet 90 °, voltage and current transformers provide LH geometric superposition after ZL rectifier bridge rectifier, supply generator field winding. When the load is supplied by the current transformers required LH compound excitation current, current compensation, the linear phase shift reactor DK phase compensation.

Second, the third harmonic principle

Sources of general generators, what we need is a sine wave frequency, called the fundamental, high than the fundamental sine wave is called harmonic, wherein the content of the third harmonic of the largest in the harmonic generator stator slots, placed There are primary winding and harmonic excitation winding (s1, s2), and no electrical connection between the windings. 150HZ harmonic winding the winding induced harmonic out, after ZL rectifier bridge rectifier, to the main generator rotor windings are excited LE.

Third, the SCR direct excitation principle

SCR direct excitation is the use of silicon controlled rectifier generator directly to any part of the energy output of a phase, after rectification to go into the field winding excitation mode, it is by the automatic voltage regulator (AVR), control thyristor conduction angle to adjust the size of the excitation current to maintain the stability of the generator terminal voltage.

Fourth, the principle of brushless excitation

Brushless excitation is mainly used for Siemens, Stanford, Rich and other brushless generator. It is the use of AC exciter, remanence or permanent magnet (with a permanent magnet machine) on the establishment of the stator voltage, the AC voltage is rectified by the starting rotation after rectification, into the field winding of the main generator, the generator build pressure. Automatic Voltage Regulator (AVR) can rapidly decrease or increase the field current according to slight deviation of the output voltage, the generator set to maintain approximately constant voltage.