Brushless Alternator-Electrical Seminar

(Electrical Engineering,Electrical & Electronics Engineering,Electromagnetic Engineering,Power Systems)

A brushless alternator is composed of two alternators built end-to-end on one shaft. Smaller brushless alternators may look like one unit but the two parts are readily identifiable on the large versions. The larger of the two sections is the main alternator and the smaller one is the exciter. The exciter has stationary field coils and a rotating armature (power coils). The main alternator uses the opposite configuration with a rotating field and stationary armature. A bridge rectifier, called the rotating rectifier assembly, is mounted on a plate attached to the rotor. Neither brushes nor slip rings are used, which reduces the number of wearing parts. The main alternator has a rotating field as described above and a stationary armature (power generation windings).

Varying the amount of current through the stationary exciter field coils varies the 3-phase output from the exciter. This output is rectified by a rotating rectifier assembly, mounted on the rotor, and the resultant DC supplies the rotating field of the main alternator and hence alternator output. The result of all this is that a small DC exciter current indirectly controls the output of the main alternator.

Advantages of Brushless Alternator are: 

1)Brushless Design 
2) No brushes or slip rings to fail.
3)No rotating windings
4) Non-Electrical unitized rotor shaft.
5)Large Diameter stator wire
6) Lower I²R winding loss.
7)Cooler stator operation
8) High amperage output.
9)High mechanical to electrical efficiency, saves fuel.
10)Replaceable diodes
11)Positive, Negative and Isolated ground options
12)Integral alternator and bearing housing casting providing permanent bearing alignment & oversize grease reservoir.

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