Publication: Doğru akım ark fırınlarının simülasyonu ve çalışma şartlarının iyileştirilmesi
Abstract
Bu çalışmada, bir Doğru Akım (DA) ark ocağının şebekeye verebileceği bozucu etkiler saptanıp, elektrik enerjisini en verimli şekilde kullanarak ucuz çelik üretimi için gerekli çözümler araştırılmıştır. Bu amaçla, bir DA ark ocağının şebekeden çektiği akım ve şebeke gerilimi üzerindeki bozucu etkileri incelenmek üzere bölgemizdeki bir çelik sanayiinde endüstriyel üretim izlenmiştir. Fabrikadaki 75 MVA gücündeki DA ark fırın elektrotlarından 90 kA civarında doğru akımın geçtiği için trafo, kontrol merkezi ve civarındaki çok kuvvetli magnetik alanlar nedeni ile gerekli ölçümler yapılamamıştır. Bu nedenle ölçümler, İTÜ Metalürji Mühendisliği Bölümü Laboratuarındaki DA ark ocağında gerçekleştirilmiştir. Bu ölçümler ile, ark fırın trafosunun alternatif gerilim ve alternatif akım dalga şekilleri, elektrotlar arasındaki doğru gerilim ve elektrotlardan geçen doğru akım dalga şekilleri hafızalı osiloskopla kaydedilmiştir. Ölçülen bu değerlerin bilgisayarla analizi yapılmıştır. DA ark fırınlarında kullanılan 6 ve 12 darbeli seri ve paralel bağlı doğrultucuların modelleri hazırlanmış ve doğrultuculara gerçek ark direnci değerlerine uygun olduğu belirlenen dirençler bağlanarak simülasyon yapılmıştır. Bu simülasyon sonucunda DA ark ocağının AA tarafındaki gerilim ve akım harmonikleri ile ark direncindeki doğru gerilim ve akım harmonikleri Fast Fourier Transformu (FFT) ile incelenmiştir. Bilgisayarda gerçekleştirilen simülasyon sonuçları ile deney sonuçları karşılaştırılmıştır. Ark fırın modelinden elde edilen sonuçlar ile bilgisayar simülasyonundan alınan sonuçlar arasında büyük benzerlikler gözlenmiştir. Sonuç olarak; ark fırınlarının şebekede meydana getirdikleri harmonik etkilerinin sadece pasif filtreler ile giderilemediği saptanmıştır. Bunun çözümü olarak, seri ve paralel aktif filtrelerin, pasif filtrelerle birlikte kullanılmasıyla harmonik etkilerinin giderilebileceği belirlenmiştir. DA ark ocağının şebekeye verdiği zararlı etkiler azaltılarak reaktif güç kompanzasyonu da yeterli bir şekilde sağlanacağından harcanan enerji miktarı azalacak ve çelik üretiminin enerji maliyeti düşecektir.
In this study, the causal effects in the network which is given by a DC arc furnace have been determined and a necessary solution has been researched for economical steel production by using the most efficient electrical energy. For this reason, industrial production at one of the steel companies in our region has been observed and experimental studies have been made in a metallurgy engineering laboratory, İTÜ. The current which is drawn from the network by the DC arc furnace and causal effects on the network voltage have been examined. Measurements have not been done because of the 75 MVA power rate of the arc furnace transformer and 90 kA current rate of the DC electrode current which causes a powerful field effect.. These measurements have been applied on the DC arc furnace in a metallurgy engineering laboratory. AC voltage and current waveforms of the arc furnace transformer and DC voltage and current waveforms between electrodes were measured and recorded by using storage a oscilloscope. These measured values have been analysed by computer. 6 and 12 pulse series and parallel connected rectifiers have been modeled and computer simulation has been done after the appropriate arc resistance value connection has been done. The results of these simulations, the current and the voltage harmonics on the AC side of the DC arc furnace together with DC arc currents and voltage harmonics have been examined by using Fast Fourier Transform (FFT). In this study, the computer simulation results have been compared with the experimental results. It has been observed that there were many similarities between the arc furnace model results and the computer simulations. As the results of the these studies show, the harmonic effects on the network which were caused by arc furnaces could not be eliminated by using only passive filters. As a solution to the problems, it has been determined that harmonic effects could be eliminated by using passive filters together with series and parallel active filters. Therefore, the harmful effects of an arc furnace on the network could be reduced and the amount of consumed energy would be decreased as a result of the sufficient reactive power compensation so that per cost for steel production would be cheaper.
In this study, the causal effects in the network which is given by a DC arc furnace have been determined and a necessary solution has been researched for economical steel production by using the most efficient electrical energy. For this reason, industrial production at one of the steel companies in our region has been observed and experimental studies have been made in a metallurgy engineering laboratory, İTÜ. The current which is drawn from the network by the DC arc furnace and causal effects on the network voltage have been examined. Measurements have not been done because of the 75 MVA power rate of the arc furnace transformer and 90 kA current rate of the DC electrode current which causes a powerful field effect.. These measurements have been applied on the DC arc furnace in a metallurgy engineering laboratory. AC voltage and current waveforms of the arc furnace transformer and DC voltage and current waveforms between electrodes were measured and recorded by using storage a oscilloscope. These measured values have been analysed by computer. 6 and 12 pulse series and parallel connected rectifiers have been modeled and computer simulation has been done after the appropriate arc resistance value connection has been done. The results of these simulations, the current and the voltage harmonics on the AC side of the DC arc furnace together with DC arc currents and voltage harmonics have been examined by using Fast Fourier Transform (FFT). In this study, the computer simulation results have been compared with the experimental results. It has been observed that there were many similarities between the arc furnace model results and the computer simulations. As the results of the these studies show, the harmonic effects on the network which were caused by arc furnaces could not be eliminated by using only passive filters. As a solution to the problems, it has been determined that harmonic effects could be eliminated by using passive filters together with series and parallel active filters. Therefore, the harmful effects of an arc furnace on the network could be reduced and the amount of consumed energy would be decreased as a result of the sufficient reactive power compensation so that per cost for steel production would be cheaper.