Typically, wind turbine couplings are stiff in the rotational axis. These torsionally rigid wind turbine couplings include wound composite tube-style couplings and disc pack couplings. These technologies allow for some angular misalignment, or cocking flexibility. Occasionally, fluid couplings are used in wind turbine drivetrains, but are size-limited without significant tooling investment. Fluid couplings allow only a limited amount of misalignment, but they are good at mitigating variations in torque loading.
A flexible coupling system, widely adopted in the drive lines of industrial off-highway equipment, such as mining trucks, can be used as a cost-effective means to reduce torque loads on bearings, while also accounting for misalignments in the drivetrain. Analysis of elastomeric couplings under normal operating conditions indicates a fatigue life greater than 20 years is achievable.
Additionally, our LCD flexible couplings slip at extremely high shock loads, temporarily decoupling the system for greater protection of the drivetrain. We have leveraged our experience in producing these couplings for applications in Antarctica in order to ensure cold weather operability for wind turbines.
Active blade pitching and power electronics are used in wind turbines to control torque and damp torsional vibrations. However, this damping may not be sufficient to protect the drivetrain in all wind conditions. By modeling a drivetrain with and without a flexible coupling, our engineers have determined a benefit exists in using the flexible coupling. Load data from aerodynamic models for a baseline 1.5 MW wind turbine were used in proprietary dynamics software.
Excessive vibration loads on the gearbox bearing nearest the highspeed shaft were identified. When modeled with a flexible coupling, this loading was reduced.
Throughout all stages of development and operation, condition monitoring equipment can be used to measure the amount of vibration on the high-speed shaft.
For new turbine designs, the basic drivetrain properties would need to be modeled to demonstrate problem vibration frequencies. Torsionally flexible couplings can be designed for the purpose of isolating vibrations, while properly placing natural frequencies of the system to avoid harmonics of the wind turbine system.