Environmental Engineering Reference
In-Depth Information
couplings may also provide for electrical current isolation, damping of torsional
vibrations, and absorb peak torques. Compact geared drivetrains, where the gear-
box and generator are combined into one mechanical
electrical power conversion
unit [29], as well as DD designs do not require fl exible couplings.
Future large turbine designs probably will not use fl exible torque coupling
technology.
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4.4.12 Signal slip ring
A slip ring is at electro-mechanical device that allows transmission of power and
electrical signals from a stationary component to a rotating component. In the case
of a WT, the slip ring electrically connects the rotating hub to stationary equipment
in the nacelle.
Future large turbine signal slip ring technology will likely be replaced with
some form of contactless system or provide for a method of producing power
onboard the rotating frame.
4.4.13 Yaw bearing and drive system
The yaw bearing performs the function of supporting the entire THM of the WT
and permitting 360° rotation relative to the turbine tower. THM includes the MH,
hub and blades. This angular yaw positioning is required to ensure the turbine
rotor is always facing squarely into the wind. The primary considerations for the
turbine designer include:
1.
Support THM relative all possible load inputs (i.e. forces and moments)
2.
Transmit rotor dynamic bending moments and loads
3.
Permit full 360° rotation times some number of turns (i.e. 2.5
before requiring
the generator electrical cable to undergo an “untwist” operation)
Minimize the amount of motor torque required to yaw while balancing the need
×
4.
for bearing joint stiffness for loads transfer, particularly wind gusts
Future large turbine yaw bearing and drive system technology may incorpo-
rate elements of bearing segments and rotor assisted yaw (i.e. “fl ying” the rotor
into the wind).
The solid line in Fig. 29 is an estimate of the industry study set trend for increasing
THM with larger WTs. The dashed line is the trend for the 10-turbine analysis group.
Future large WTs in the 7
10-MW size range will need THM to be targeted for the
solid line or lower to ensure favourable WPP economics. As can be seen, some of
today's 4
−
5 MW size machines are considerably above the solid line, which is indic-
ative of excessive THM and potentially poor economic performance. Provisioning a
yaw bearing and drive system for excessively large THM only adds to the problem.
Achieving the lowest possible THM is a key design driver for the yaw bearing and
drive system, as well as for the tower support structure (among other considerations).
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4.4.14 Nacelle and nose cone
Today's nacelle and hub fairing (i.e. nose cone) are typically manufactured from
GFRP. These are generally non-structural and protect the drivetrain components
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