After a design and construction phase of less than 2 years, Schaeffler today officially put the world’s largest, most up-to-date and most powerful large-size bearing test stand into operation at its Schweinfurt plant. The test stand enables large-size bearings of up to 15 tons and measuring up to 3.5 meters such as those used in wind power applications in particular to be tested in realistic conditions using a comprehensive simulation program. This means Schaeffler is making a major contribution to shortening development times for wind turbines as well as making the design process more reliable and increasing the cost-effectiveness and safety of these turbines. At around #8364;7 million, the Schaeffler large-size bearing test stand is a significant investment in the further development of renewable energies and the company’s development location in Schweinfurt.

The new test stand will primarily be used for testing rotor bearing supports for wind turbines in the multi-megawatt class and will result in further improvements in the understanding of systems as a whole, influencing factors and the interrelations in the drive trains of wind turbines. This will result in optimized bearings characterized by lower friction and increased design safety. In addition, the tests will provide information about and recommendations for wind turbine operation and maintenance as well as for optimum adjacent constructions.

For example, the test stand carries out realistic simulations of static and dynamic forces and torque that act on the rotor bearings and slewing rings. All rotor bearing support concepts for wind turbines with an output of up to 6 megawatts can be tested on the test stand. Functional tests provide insights into the rolling bearing kinematics, temperature and friction behavior, loads and deformation. The data required for these tests is supplied by more than 300 sensors on and in the bearings.

The test stand has been named “Astraios” after a Titan in Greek mythology who was father of the four wind gods.



Shortening development times and making the design process of wind turbines more reliable: The world’s largest, most up-to-date and most powerful large-size bearing test stand enables large-size bearings of up to 15 tons and measuring up to 3.5 meters such as those used in wind power applications in particular to be tested in realistic conditions using a comprehensive simulation program.

Setup and function of the large-size bearing test stand

The loading frame is the most important component of the test stand. Four radial and four axial hydraulic cylinders are fixed to the frame, which generate the real loads and moments that occur in a wind turbine. The radial cylinders simulate the weight of a rotor hub with rotor blades while the axial cylinders generate the wind loads.

The rotors and hub in large turbines can weigh more than 100 tons. This weight acts on the bearing and generates a so-called static radial load and a static nodding moment. Accordingly, the four radial cylinders have impressive dimensions, since each cylinder can generate a maximum of one meganewton of force, which is equivalent to 100 tons of weight.

The axial cylinders have even more “power", since they can provide up to 1.5 meganewtons for simulating the static axial load as well as the dynamic pitching and yawing moments. This pitching and yawing is comparable to the lifting and lowering and turning of the nacelle.

Various wind speeds can be simulated using the drive train and planetary gearbox. Typical speeds are between four and 20 revolutions per minute and speeds up to 60 revolutions per minute are possible. The tensioning frame represents the connection side of the wind turbine's nacelle.



The four radial and four axial hydraulic cylinders (right-hand side of the picture), which generate the real loads and moments that occur in a wind turbine. The radial cylinders simulate the weight of a rotor hub with rotor blades while the axial cylinders generate the wind loads.

It’s a well-known fact that the wind seldom blows at the same speed or from the same direction. In fact, it acts with varying intensity and at different points on the wind turbine. Varying moments are generated on the rotor hub, depending on the position of the rotating rotor blades. If, for example, the wind acts on the top or bottom of the rotor blades, it generates the so-called dynamic nodding moment. This is supplemented by so-called dynamic yawing moment if the wind turns and blows more strongly from the side.

These factors all mean that wind turbines are subject to extremely complex conditions due to the continuously changing wind conditions. This is a Herculean task, not only for the test stand and the 8 hydraulic cylinders that simulate all real loads and moment, but also for SARA that automatically controls the comprehensive measurement, open loop and closed loop control processes. SARA stands for Schaeffler Automation System for Research & Development Applications.

SARA generates the target values in accordance with the wind loads, controls the highly-dynamic servo cylinders, controls all units, ensures all data is measured and stored, is responsible for telemetric bearing measuring technology, displays all target, actual and limit values, evaluates measured data, and generates logs.

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