Environmental Engineering Reference
In-Depth Information
level of fi eld assembly to meet all of the logistics and crane requirements. Achieving
the lowest possible MHM while still delivering all of the functional and opera-
tional needs is a fundamental design goal, and it will require new technologies and
innovative integration approaches to develop an economical large WT MH.
4.4.7 Gearbox
A gearbox is needed to transmit torque and increase blade rotor rotational speed
to match the requirements of an electrical generator. Today's high-speed generator
technology requires speeder gear ratio of 1:100 or more. Torque transmission must
be done with limited vibration and noise effects. Mechanical effi ciencies have to be
as good as economically feasible in order to minimize power losses in the system.
An emerging form of gearbox is a compact geared drivetrain where planetary
gearing and medium speed (speeder ratios of 1:30 to 1:40) generator technolo-
gies are combined into one mechanical
electrical system. The integrated geared
generator is lighter and more compact than conventional three-stage gearbox
−
generator
systems and, with fewer gears and bearings, is both more reliable and more
effi cient [ 29 ].
Future large turbine gearbox technology will likely incorporate elements of
lower overall gear ratio, reduced number of stages, or elimination of the gearbox
altogether.
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4.4.8 Drivetrain dynamics
Today, WT drivetrains undergo signifi cant loading during WT operation due to
changes in environmental conditions, such as wind gusts. Future large turbine drive-
train dynamics technology will likely incorporate elements of adaptive response
and control. As speed control technology improves, loads on the drivetrain may be
reduced, improving reliability [56].
4.4.9 Rotor lock - low-speed and high-speed shafts
A rotor lock is a device that prevents shaft rotation. In the case of a main shaft or low-
speed shaft, the rotor lock is used during construction and during maintenance of the
WT. The high-speed rotor lock is used to prevent rotation of the gearbox output shaft.
Future large turbine rotor lock technology will likely be replaced with some
form of distributed system, and DDs obviate the need for a high-speed rotor lock.
4.4.10 Disk brake system and hydraulics
Future large turbine disk brake system and hydraulics technology will likely
incorporate elements of integrated generator brake design or elimination of the
disk brake system altogether due to advances in more reliable blade operation and
advanced rotor controls.
4.4.11 Flexible torque coupling
Shaft couplings are used to transmit torque from one shaft to another, as is the case
for today's designs that incorporate a gearbox and separate generator. Flexible
couplings are used to balance radial, axial, and angular displacements. In addition,
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