Gearboxes give way to Direct Drive Turbines
Many turbine manufacturers are moving towards direct drive turbines and leaving the traditional
gearbox turbines behind. Direct drive turbines achieve more reliability, efficiency and reduce the
overall cost of producing electricity. In a direct drive method, power is taken directly from the
mechanical source without any efficiency reductions earlier caused by a gearbox.
Direct drive mechanisms have always been around. They have had mechanical advantages
over traditional methods but since they came with a high price tag and were huge in size,
they never really posed as a threat for the gear box turbine manufacturing process. But many
bigger corporations like Siemens and PM Generators Ltd. have come up with new designs and
technology where turbines are directly connected to permanent magnet generators. The overall
arrangement has resulted in a lighter and affordable model.
The Direct Drive has its reasons to become popular:
• More efficient – No power wastage from belts, chains, gearbox etc
• Drive Stiffness – Avoiding gearbox results in removal of mechanical backlash, hysteresis
and elasticity
• High torque is obtained even at low speed
• Noise reduction – Fewer components and friction reduce overall noise
• Increased lifetime – Less parts result in less failures and increased performance
In a traditional gearbox mechanism, the blades rotate and the shaft connected to it provides the
turning speed to the generator through a gearbox. A rotation speed of about 1500 rpm generates
required electricity. A typical wind turbine will rotate at less than 300 rpm. To increase the
rotations to 1500 rpm, energy is loss in the process. The inner components of the gearbox are
prone to tremendous stress. Eliminating this part simplifies the operation to a larger extent and
makes it easier to maintain for a long period of time. This is especially important for offshore
wind farms because doing maintenance at sea is a lot more complex and expensive than on the
ground.
