Availon O&M workers on the job.

Companies that insure wind turbines would like to influence the trends here. For instance, they suggest, get more than one quote for a repair job and don’t feel obligated to accept the one from the OEM. Other industries consider one quote inadequate. What’s more, ISPs might react faster to an offline turbine than would an OEM. These actions can result in lower claims costs which will reduce annual premiums.

Other trends need changing as well. For instance, after a wind tech identifies an ailing component on a turbine, the natural reaction is to replace it with a recommended version from the OEM. But when they stop supporting a turbine or a complex outsourced component, maintenance crews are forced to look elsewhere. Those OEM business decisions have initiated the rise of repair services.

A growing trend in the larger O&M scheme of things has wind turbine maintenance companies looking for repair services to support their work. Commonly repaired components include printed circuit boards, pitch drive systems, inverters, IGBTs, PLCs, VRCC units, AEBIs, proportional valves, hydraulic pumps, pitch and yaw motors, encoders, slip rings, transducers, and more.

This trend toward rebuilt parts is becoming more pronounced because the independent service providers (ISPs) tend to improve on what turbine OEMs have designed. For instance, one ISP says repair prices are typically half the cost of new parts and a good reason to consider repaired parts. To some extent, OEMs encourage the trend when they no longer support their equipment. This encourages repair ISPs to drive other trends, such as:

Rebuild, not just repair – The companies in this space caution that “repair” is a general term implying the repaired part is as good as the old part. More than simply repaired to OEMs specs, the companies say they have taken the time diagnose problems and improve on original equipment. The most common product upgrade performed, according to one company, is to printed circuit boards. This ISP says when it is working on a Clipper Xantrex Matrice, the company provides new cables, cleans and machines heat sinks so they adhere tightly to a new waterproof gasket, polishes IGMT mating surfaces for an improved thermal junction with the heat sink, adds fault protection circuitry to the advanced IGBT driver modules, and uses a new generation of IGBTs.

Upgraded components – This is the big trend. One engineering service firm enhances legacy components with newer, more reliable technology to improve performance and extend the component’s life. The company says it uses the latest diagnostic tools to detect failures down to the microchip.

Two widely used products that get upgrades are the GE 1.5 MW S Series Xantrex Matrix Inverter and the Clipper 2.5 MW Xantrex Inverter. These drop-in replacement designs let wind farms supplement shrinking inventories with more dependable, longer-lasting products, while keeping the turbines online. The effort is to provide comprehensive remanufacturing services for unsalvageable, obsolete components.

Reduced inventories – When components are readily available, O&M crews need not maintain inventories in their own facilities which further trims their costs.

Longer warranties – With improved replacement components, ISPs can warranty more equipment with longer warranties than the original equipment carried. One says it warrants rebuilt parts for 18 months from time of purchase.

Emergency services – These involve maintaining stock of many surplus parts to help clients get production equipment back up and running. ISPs offers component repair along with engineering services for GE, Vestas, Siemens, Clipper, and other wind turbines.

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Several trends here are toward more reliable designs in new turbines and in replacement units. In the aftermarket, custom designs meet client specs, slip rings are available for non-supported machines, and combination devices for transmitting power, signals, and fluids. “New solutions are needed to replace older technology slip rings in turbines with long-life, high-reliability designs that can operate for years without maintenance,” says Moog’s Senior Business Development Manager Steve Black.

For pitch functions, the ideal slip rings would be installed and forgotten. Many designs in use today require periodic maintenance to clean away wear debris, flush out oil and dirt, and relubricate. In pitch slip rings, design trends are on at least two fronts. “First, as turbine designs increase in power output and size, the demand on the pitch slip ring is for higher power transfer,” says Black. “Second, data handling and signal demands are increasing to provide additional condition monitoring in the hub. It is critical that the contact technologies be durable enough to handle power peaks at the extremes of operation.” More complete pitch control is another trend. These would include hub controls, pitch-drive motors, power back-up, blade monitoring, and slip-ring channels to transfer the power and control signals through the rotary interface.

A quest for higher reliability has encouraged some companies to devise non-contacting slip rings. At least two companies are at work here developing inductively coupled power transfer devices. One manufacturer says its slip rings work at high efficiencies by using wireless power transfer that can harmonize itself in the field. The company says this makes the systems resistant to changes in environmental conditions and load variations. Power transmits as a single load while a built-in, data-communications system switches power, for example, to meet different device requirements of wireless receivers.

Collaboration is another trend. One ISO is partnering with a slip-ring manufacturer to design, manufacture, and distribute slip rings. Manufacturer UEA says it provides its slip rings as completed, ready-to-mount assemblies with optional pre-wired harnesses. The goal is to reduce up-tower time so the company makes a wide selection of circuitry available, with many combinations of amperage and voltage, ac or dc. The compact design is made possible by stacking brushes on alternating sides. The slip rings come in bore sizes from 0.500 to 14.00 in. UEA President Mark Hanawalt says his company’s custom-designed wind turbine slip rings match customers specs and can be delivered in a matter of weeks.

UEA recently designed an improved slip ring for Clipper wind turbines. It’s more reliable, says Hanawalt, with improved sealing, removing the exposed external wiring, and enhancing the communication circuits. For instance, a new ball bearing design significantly improves bearing life over the original design, which required more delicate handling.

Trending offshore — Manufacturer Deublin says its off-shore wind turbine union includes a slip ring and encoder. Units for off-shore and on can deliver up to 250A, transmit Ethernet and Profibus signals, resist shock and vibration, and provide a protection class IP 54-IP66. Add a rotary union and device accommodates hydraulics, electrical power, EtherCAT, and rotary position information. “Offshore turbines will require more reliable components due to their remote locations. Cost and time of reaching the offshore turbine is significant compared to most of the onshore turbines” says Jerry Lichter, Senior Product Engineer at Deublin.

Lastly, custom designs and combination units — Building blocks allows solving design challenges such as RF shielding, mixed signal handling, high-frequency-impedance matching, reduced temperature generation, and miniaturization, says Deublin. The company adds that its plug-and-play slip ring and union combination reduces installation and maintenance time because electrical and hydraulic connections are plugged or unplugged as part of the installation or removal process rather than having to disconnect those cable connections and hose fittings separately. Other options include absolute or incremental encoders, optical rotary joints for fiber optical connection, even an internal heater for use in cold weather.

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Clipper Winpower manufacturers the 2.5 MW Liberty wind turbine.

Connecticut-based United Technologies had previously owned 49.9% of the stock in Clipper Windpower and apparently has purchased all remaining shares. “Its acquisition by UTC creates the long-term financial stability necessary for Clipper’s continued growth, while enabling Clipper to fully leverage UTC’s management capabilities, operational expertise, and world-class technology in blades, turbines, and gearbox design,” read a statement by UTC.

Clipper Windpower has headquarters in Carpinteria, California and manufacturing facilities in Cedar Rapids, Iowa. It produces the 2.5-megawatt Liberty wind turbine. Since June 2006, it has had orders to provide 2,240 units of the Liberty machine. The company also has a presence in the UK, where it is developing a much larger wind turbine for offshore wind farms, the Britannia, which is to have a nameplate capacity of 7.5MW and eventually 10 MW.

United Technologies Corp.

www.utc.com

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