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7 ZAKLJU»AKU radu je opisan model transformatora primjenjivu prijelaznim pojavama relativno niskih frekvencija.Za energetske transformatore velikihsnaga pokazano je da se krivulja magnetiziranjakvalitativno moæe predstaviti preko dva pravca.Pokazane su granice upotrebe analitiËkih metodaproraËuna prijelaznih pojava u transformatorima.Za numeriËko rjeπavanje sustava krutih diferencijalnihjednadæbi iskoriπteno je implicitno trapeznopravilo. Razvijeni algoritam je moguÊe apliciratiu niskofrekvencijskim prijelaznim pojavama kaoπto su: uklapanje transformatora, ferorezonancija,ispad tereta, kvarovi transformatora itd. Na krajuje pokazan primjer upotrebe realiziranog algoritmana proraËun prijelazne pojave uklapanja trofaznogtrostupnog transformatora. Kompariranjemmjerenih i simuliranih struja uklapanja trofaznogtransformatora ustanovljeno je da se pogreπke nalazeu zadovoljavajuÊim granicama (maksimalno3,56 %).7 CONCLUSIONA transformer model applicable to relatively lowfrequency transient phenomena is described in thearticle. For power transformers with high power ratings,it was demonstrated that the magnetizing curvecan be adequately presented with two straight lines.The limits for the use of analytical methods for thecalculation of transient phenomena in transformersare presented. The implicit trapezoidal rule wasused for the numerical solution of a system of stiffdifferential equations. The developed algorithm canbe applied to low frequency transient phenomenasuch as transformer energization, ferroresonance,load switch-off, transformer faults etc. An exampleof the application of the developed algorithmwas presented for the calculation of the transientsthat occur during the energization of a three-phase,three-legged transformer. Through comparison ofthe measured and simulated inrush currents of thethree-phase transformer, it was established that theerrors were within acceptable limits (a maximum of3,56 %).TokiÊ, A., UglešiÊ, I., NumeriËki proraËun niskofrekvencijskih..., Energija, god. 56(2007), br. 5., str. 584-607TokiÊ, A., UglešiÊ, I.,The Numerical Calculation of..., Energija, vol. 56(2007), No. 5, pp. 584-607606