Drives & Controls October 2022

n TECHNOLOGY October 2022 www.drivesncontrols.com 24 A TEAMOF 35 Danish engineers has started work on what will be the world’s most powerful test bench for wind power components when it is completed in 2024. The 60m-long test bench, incorporating two 30MW motors, and weighing 5,700 tonnes, will also be the world’s largest. The facility – to be installed at ZF Wind Power’s Test & Prototype Centre in Lommel, Belgium – will be able to simulate the most arduous conditions that the world’s largest offshore wind turbines might experience. It will simulate varying loads on nacelle components including gearboxes and drivetrains. Using Halt (highly accelerated lifetime testing) techniques, prototype wind turbines will be exposed to the equivalent of 20 years of operation in extreme weather conditions in a few months, to discover the limitations of the turbine designs and to determine their reliability. “Wind loads, and directions, can vary greatly, and each change creates loading on the nacelle powertrain,” explains Ralf Nieschler, key account manager at the Danish wind turbine test specialist, R&D Test Systems, which is developing and building the facility. “This new test rig must be much more powerful than the powertrain it tests, providing proof that the next generation of offshore turbines – of say, 20MW – are capable of operating reliably in extreme offshore conditions. “The force of gusts wind can be a bit like a herd of elephants, pushing the blade around,” he adds. “This twisting and bending of the powertrain in all possible directions in the test rig will simulate the effect of 20 years of wind conditions in just a few months.” The two 30MW motors at either end of the rig will allow two nacelle components – for example, two powertrains or two gearboxes – to be tested simultaneously, leading to significant time savings. In addition, a load system between the nacelle components will simulate wind loads that might be encountered in the real world. It will be able to replicate not only the harshest wind loads, but also the effects of wind coming from different directions. The rig will be able to produce a drive torque of 45MNm – equivalent to dangling 30 cars from the end of a 100m-long turbine blade – as well as bending moments of up to 64MNm. The team working on the project includes electrical, systems, software and mechanical engineers. Civil engineering expertise will also be needed for the reinforced concrete foundations that will need to withstand extreme fatigue and wind loads during the tests, as well as carrying the weight of the test rig and of the powertrain under test which could add several hundred tonnes. The rig will be transported from Denmark to Belgium in modules. Part of the project is a 300-tonne lifting capacity crane for mounting powertrains onto the rig. 60MWwind turbine test rig will be world’s most powerful THE ENGINEERING PLASTICS specialist igus has developed a plastic ball bearing that unusually combines two materials to make it wear-resistant and dimensionally stable and quiet, even at high speeds. This design makes the xiros 2K bearing suitable for use in applications such as fans and lab equipment. When ball bearings operate at high speeds, they need materials that can withstand high centrifugal forces. But these hard materials, when used with stainless- steel balls, lead to high levels of vibration and noise. The new two-part lubrication- and maintenance-free plastic ball bearing ensures quiet operation, even at high speeds. The noise-dampening effect is provided by a layer of blue xirodur D180 material. To give this soft, wear-resistant inner material a high dimensional stability, it is combined with a hard shell. Because the soft material is poured into the hard shell of both rings, the balls always run on the soft, high- performance plastic when rotating and are supported by the shell. Undercuts in the balls ensure high adhesion of both materials and stability. The balls are kept apart by a wear-resistant cage made of the iglidur J3 plain bearing material. Compared to standard ball bearings, the new bearing achieves particularly quiet, smooth operation at high speeds. Tests have shown that the noise levels are around three times lower at high speeds than for standard xiros bearings. “In the tests, the new xiros 2K bearing proved to be nine decibels quieter, which corresponds to about half the volume of a B180 ball bearing,” reports igus UK’s Drytech director, Rob Dumayne. Unlike metal bearings, the tribologically- optimised plastic bearing does not need external lubrication to maintain its smooth running. Despite the lack of lubricants, the bearing has a long service life with low running costs. It will be available initially with an inner diameter of 10mm. Versions from 5–12mm are planned. Customised versions will be possible. An online configuration tool for the xiros 2K bearing is being developed. www.igus.co.uk Novel two-part ball bearings cut noise levels, even at high speeds An computer-generated impression of what the finished 5,700-tonne wind turbine test rig will look like