In conventional DC machines, the field is on the stator and the armature is on the rotor. The
stator comprises a number of poles which are excited either by permanent magnets or by
DC field windings. If the machine is electrically excited, it tends to follow the shunt wound
DC generator concep. An example of the DC wind generator system is illustrated in Fig. 6. It consists of a wind
turbine, a DC generator, an insulated gate bipolar transistor (IGBT) inverter, a controller, a
transformer and a power grid. For shunt wound DC generators, the field current (and thus
magnetic field) increases with operational speed whilst the actual speed of the wind turbine
is determined by the balance between the WT drive torque and the load torque. The rotor
includes conductors wound on an armature which are connected to a split-slip ring commentator.
Electrical power is extracted through brushes connecting the commentator which
is used to rectify the generated AC power into DC output. Clearly, they require regular
maintenance and are relatively costly due to the use of commutators and brushes.
In general, these DC WTGs are unusual in wind turbine applications except in low power
demand situations [47; 23; 33; 54] where the load is physically close to the wind turbine, in
heating applications or in battery charging.
In conventional DC machines, the field is on the stator and the armature is on the rotor. The
stator comprises a number of poles which are excited either by permanent magnets or by
DC field windings. If the machine is electrically excited, it tends to follow the shunt wound
DC generator concep. An example of the DC wind generator system is illustrated in Fig. 6. It consists of a wind
turbine, a DC generator, an insulated gate bipolar transistor (IGBT) inverter, a controller, a
transformer and a power grid. For shunt wound DC generators, the field current (and thus
magnetic field) increases with operational speed whilst the actual speed of the wind turbine
is determined by the balance between the WT drive torque and the load torque. The rotor
includes conductors wound on an armature which are connected to a split-slip ring commentator.
Electrical power is extracted through brushes connecting the commentator which
is used to rectify the generated AC power into DC output. Clearly, they require regular
maintenance and are relatively costly due to the use of commutators and brushes.
In general, these DC WTGs are unusual in wind turbine applications except in low power
demand situations [47; 23; 33; 54] where the load is physically close to the wind turbine, in
heating applications or in battery charging.
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