SOLUTIONS - Moeller Electric Parts

SOLUTIONS17SOLUTIONS18THE COMPANYWoodward SEG GmbH & Co. KG isbased in Kempen on the Lower Rhineand supplied its first frequency inverterfor a wind turbine generator at theend of 1996, at that time under theSEG logo. As SEG, the company hasalmost 40 years of experience in thepower distribution and protectiontechnology. Frequency inverter seriesproduction for the German market wasdeveloped rapidly from smaller pilotseries and also for the US market since2000. The “saturation” of the Germanwind power market from 2002/ 2003led frequency inverters from Kempenworldwide into other growing windpower markets: In countries such asFrance, Spain, Great Britain, as well asJapan, China and Australia they areconverting wind power into electricitytogether with the generator - on landand sea. Up to now more than 5000inverters have been installed for systemcapacities between 600kW to 5MWand also for larger capacities in future.(www.woodward-seg.com).inverter is switched into the rotor circuitof the asynchronous generator in order toregulate the system output according to therotor speed. IGBTs (insulated-gate bipolartransistor) generate a voltage with a variablefrequency and amplitude from a DC linkcircuit. The frequency in the rotor circuitis set according to the speed of the WTG,which depends on the wind. The stator of theasynchronous generator is connected to themedium voltage network via a circuit-breakerand transformer.Alternative connection to the gridThe speed range of wind turbine generatorsis more often in the lower range than inthe rated range. This means that circuitbreakershave to be switched on and offvery frequently. Added to this are the safetyrequirements which must be observed in theconnection to an industrial network withshort-circuit currents of up to 50 kA. Reducingthe number of switching operations reducesmaintenance costs as well as downtimes. Ifoperating currents of present day WTGs areto be controlled between 2000…3000A andswitched in the event of a fault, series circuitsconsisting of circuit-breakers and contactorsoffer a very good technical and yet veryexpensive solution. However, these kinds ofsystems are primarily considered from thepoint of view of costs, and so a cost-optimisedcircuit should also be used not least for thesereasons.There is, however, another solution. A“smaller” bypass consisting of an NZM (-Q2)circuit-breaker and (K2) contactor for the“main switch Q1” can handle the connectionto the grid in the partial load range. Even highshort-circuit currents with grid transients arecontrolled by the combination of softwarebasedcurrent monitoring and vacuum tubetechnology offered the DILM contactor. Theshort-circuit protection of the bypass circuit isimplemented with an NZMH4 circuit-breaker.Practical experience with this circuit to datehas shown that the switching operations ofthe main switch can be reduced with a bypass.An experienced team, consisting of specialistsfrom Woodward SEG and Moeller testedthe use, dimensioning and function of thecircuit and assessed the risk in the form of afailure mode and effects analysis (FMEA). Theresults of the analysis were impressive in everyrespect.Highly efficient switching up to 2200A with Moeller DILH contactors. The vacuum technology preventsexposed arcing and allows a considerably longer electrical lifespan compared to air contactors. The 2500 Arating class will be added to the series in futureA bypass to the main switch consisting of compactcircuit-breaker and vacuum contactor handles theconnection to the grid in the partial load range.CONCLUSION“Our customers have trust in ourtechnical solutions. We are continuouslyoptimising our frequency invertersand thus also reducing the life cyclecosts of the WTGs. In this respect weconsider ourselves at Woodward SEG astechnical partners of our customers,”team leader Eric Harmann explainedabout the use of Moeller components.“We are very happy with Moeller‘stechnical support. The understandingof a system for wind power technologycan only be achieved on the basis ofcontinuous cooperation. In my opinion,our strengths are in the search forcommon and well-founded solutions.”Quicklink ID:MS1818For Moeller Electric Sales and Support call KMparts.com (866) 595-961627