sin αst

GENERATOR AND ELECTRICAL SYSTEM
A key advantage of the chosen generator design is that it operates at low rotational veloci-
ties compared to typical asynchronous generators, hence making it possible to utilise a
direct drive concept without any transmission. An additional advantage is that the genera-
tor can be built locally on-site, which facilitates production of replacement parts and in-
creases the design flexibility in that details may be changed to comply with varying local
needs.
As the name implies, the magnetic field of the axial flux permanent magnet generator is in
the axial direction, contrary to prevailing generators which have radial magnetic fields.
The generator output is 3-phased wild AC, referring to the varying output frequency and
voltage due to the variable speed of the wind turbine rotor. A rectifier, described in section
7.2, converts the wild AC into 48 V DC in agreement with the requirement of table 2.1.
Design of the generator, e.g. the sizing of magnets, wire dimensions and coils, is beyond the
scope of this project. However, since the generator has high influence on the overall wind
turbine design, its components, performance and loads it is necessary to establish a realis-
tic generator for the purpose design and calculation. This is done by using the dimensions
and principal layout of an existing commercial axial flux generator (att. 10) in the design
and by defining a characteristic for the generator which is achievable.
The generator consists of three main parts: stator, rotor and shaft as shown on the pro-
posed layout drawing of figure 7.1.
Figure 7.1: Cross section of the axial flux generator
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