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MATERIALS Turbines embrace


A rethink of the materials used for main wind turbine slip-rings increases reliability resulting in lower risk of downtime and unplanned maintenance, according to Morgan Advanced Materials


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eliance on wind power is increasing so the industry must continue to find ways to operate more efficiently while reducing maintenance and costs. One key to wind energy lies in the turbine’s slip rings, says


George Finley, wind segment manager from the Electrical Carbon business of Morgan Advanced Materials. In the USA, there are currently around 58,000


wind turbines generating a total rated capacity of 91,115MW but the US Department of Energy projects that this will increase to more than 400,000MW by 2050. This dramatic rise is down to a swathe of onshore developments in Arkansas, Nebraska, New Mexico, South Dakota and Wyoming. These wind farms will be joined by offshore projects in Maryland and Massachusetts. With this huge increase in power generated by


wind, in turn the number of people that rely on this source of energy will also go up – making it integral that downtime, maintenance and operating costs are kept to a minimum.


IN WITH THE NEW In addition to the sourcing of electricity, the maintenance practices of wind turbines are also undergoing a shift. In past years, maintenance engineers have often taken a reactive approach, dealing with problems and failures as they arise. Increasingly, though, operators are realising the severe cost implications of responsive repair methods and are looking to a more preventative approach. Like many industries, the wind power sector is


already harnessing emerging technologies to anticipate problems before they occur, such as simulation software, drones and optimisation. These technologies are set to improve rapidly, as even the world’s largest technology companies are investing in wind power to increase their green credentials and profits. Yet it’s not all about digital technologies. Despite


progress in automated diagnostic systems, sometimes there is no substitute for experienced engineers and technicians that are able to spot the


26 /// Testing & Test Houses /// June 2019


tell-tale signs of turbine failure. One such example lies within the mechanics of the turbine’s slip ring and brush system.


THE RING OF POWER Slip rings are used to collect rotor current and send this to the grid. They are often made from solid metals and used in conjunction with carbon brushes, usually made from graphite combined with metals such as copper or silver. As the rotor of the turbine generator rotates, so


does the slip ring. The electrical current produced by the rotor is conducted through the rotating slip ring to the carbon brushes, held in optimum position by static brush holders with springs which allow the brushes to move and stay in contact with the rotating slip ring.


GONE IN A FLASH It is integral that brushes are held in place with good stability, as instability, known as friction chatter, can occur. This causes a loss of contact between the brush and slip ring interface, which can lead to


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