Environmental Engineering Reference
In-Depth Information
Vgen
cable
resistance
winding
resistance
charge
control
DC
generator
Vbatt
Battery
Figure 13: Simplifi ed battery charging circuit.
Figure 14: Relative impact of rotational speed on maximum rotor power.
Besides not needing a gearbox, DC systems can use the permanent magnet gen-
erator as a brake. The windings need only be shorted or connected across a small
resistance, and this results in signifi cant braking torque from the generator. It is
typical for DC machines, during the commissioning process, to have their winding
shorted until such time as the turbine is ready to rotate.
1.3.2 AC systems
1.3.2.1 Permanent magnet alternator with grid-tie inverter
This approach is commonly used for machines up to about 10 kW to produce
grid-quality AC power. Above this level (and sometimes below), a gearbox
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