Transtech Power Transmissions


Wind Energy

Wind Energy Drives (WED) are a new range of gearboxes for wind turbines that ensure low maintenance and long operational reliability. Our range of wind turbine gearboxes use epicyclic gear trains that employ Trans-Flex® technology, guaranteeing equal load distribution along the gear teeth and between the multiple meshing points. Using a Trans-Flex® system gives optimal gear meshing between the planet gears and respective sun and ring gears, reducing friction, wear and noise levels. 

Our solution allows the maximum number of planet wheels and differentially divided power flow via two paths through the gearbox. This compact gearbox design significantly lowers mechanical stress on the gear teeth and bearings as well as making a torsionally flexible transmission.


The original design has proven its reliability over several years in service in one of the oldest and largest turbines in the world. In 1987, at Burgar Hill in Orkney, Scotland, an experimental three megawatt wind turbine was installed using flexible pin technology. 13 years later (due to generator failure), the entire turbine was dismantled. It held the record for the most powerful onshore machine in the UK.

The flexible pin concept was invented in the early 1960s. The final analysis of the Orkney turbine’s gearbox, done in 2000, showed no damage or unexpected wear in the gear trains. Based on these findings and our own extensive experience in supplying epicyclic gear systems for offshore and marine applications, we decided to pursue the wind turbine market.

Transtech has further improved the flexible pin concept and this Trans-Flex® technology produces the optimal gearbox design for wind turbines.

Principle sketch showing the Trans-Flex® system.



The variable ratio system (VRS) keeps the generator at a constant regardless of the wind speed. The mechanical/hydraulic method of achieving this constant speed makes the installation cost effective. In addition, the VRS performs as a safety device in the drive train by actively controlling the transmitted torque. 

Because of the way modern turbine rotor blades react during wind gusts, transient speed changes occur that induce torque fluctuations in the gearbox. The referred generator inertia and the magnitude of such torque transients is the likely cause of the high rate of failure in traditional rigid gear driven turbines. Also, it is imperative to consider the turbine’s rotor diameter; the larger it is, the slower it rotates and the more aerodynamic power transients will occur. A lower rotor RPM requires a higher gear ratio to keep the optimal generator speed. As the referred generator inertia is calculated by multiplying the generator inertia by the square of the gear ratio, it is evident that the problem increases exponentially with the size of the wind turbine.


Currently we have three models available: 

WED 650 (650 kW); WED 1400 (1.4 MW); and WED 3400 (3.4 MW).
The 650 and 1400 have a fixed ratio; the 3400 is variable.

The Transtech WED gearbox is designed for long operational reliability and has a large number of advantages:

• Smooth power transfer from turbine to generator
• Minimal maintenance requirements
• Compact; can be placed in existing nacelles
• Shaft mountable
• Hydraulic operated inching
• Forced lubrication including cooling system
• Lightweight
• Temperature sensors
• Economical to produce
• Adjustable peak limiter
• Optional variable ratio system

The range of Transtech WED gearboxes can easily be modified to fit into any existing or newly designed wind turbine.