Civil Engineering Reference
In-Depth Information
6
Electrical G
enerator
6.1
Electromechanical Energy Conversion
The conversion of the mechanical power of the wind turbine into the elec-
trical power can be accomplished by any one of the following types of the
electrical machines
:
•
the direct current (DC) machine.
•
the synchronous machine.
•
the induction machine.
These machines work on the principles of the electromagnetic actions and
reactions. The resulting electromechanical energy conversion is reversible.
The same machine can be used as the motor for converting the electrical
power into mechanical power, or as the generator converting the mechanical
power into the electrical power.
Figure 6-1
depicts common features of the electrical machines. Typically,
there is an outer stationary member (stator) and an inner rotating member
(rotor). The rotor is mounted on bearings fixed to the stator. Both the stator
and the rotor carry cylindrical iron cores, which are separated by an air gap.
The cores are made of magnetic iron of high permeability, and have conduc-
tors embedded in slots distributed on the core surface. Alternatively, the
conductors are wrapped in the coil form around salient magnetic poles.
Figure 6-2
is the cross-sectional view of the rotating electrical machine with
the stator with salient poles and the rotor with distributed conductors. The
magnetic flux, created by the excitation current in one of the two members,
passes from one core to the other in the combined magnetic circuit always
forming a closed loop. The electromechanical energy conversion is accom-
plished by interaction of the magnetic flux produced by one member with
the electric current in the other member. The latter may be externally sup-
plied or electromagnetically induced. The induced current is proportional
to the rate of change in the flux linkage due to rotation.
