Amorphous çekirdekli transformatörün incelenmesi ve tasarımı
Amorphous alloy core distribution transformers
- Tez No: 75416
- Danışmanlar: PROF. DR. NURDAN GÜZELBEYOĞLU
- Tez Türü: Yüksek Lisans
- Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Elektrik Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 85
Özet
ÖZET Bu çalışmada; amorphous malzemenin özellikleri, transformatör sanayinde kullanılabilirliği, geleneksel demir çekirdekli transformatörle karşılaştırılması ve elektrodinamik kuvvetlere olan duyarlılığı ele alınmıştır. Bunun için, aynı güçte amorphous çekirdekli ve demir çekirdekli iki transformatör tasarlanmış, imal edilmiş ve sonuçları kıyaslanmıştır. Bu iki transformatörün aynı zamanda aksiyal ve radyal kuvvetleri de hesaplanmıştır. Normal çalışma koşullar altında amorphous çekirdekli transformatörün üstünlükleri ve zayıf yönleri ele alınarak, şu anki teknolojinin elverdiği ölçüde kullanılabilirliği tartışılmıştır. Bu tez çalışmasında; amorphous çekirdekli transformatör geleneksel demir çekirdekli transformatörle karşılaştırıldığında, boyutlarının daha büyük olduğu ve daha fazla işçilik içerdiği, buna rağmen boşta kayıplarının çok düşük olduğu saptanmış, bu özelliğiyle, geleneksel demir çekirdekli transformatörlere göre avantaj sağladığı belirlenmiştir. Aynı zamanda bu çalışmada aksiyal ve radyal kuvvetler üzerinde durulmuş ve amorphous malzemenin dayanımı açısından büyük kuvvetlere maruz kaldığı tespit edilmiştir. Amorphous çekirdekli modelin dayanımının kuvvetlendirilmesi amacıyla, fazla izolasyon malzemesinin kullanılması sargı seri ve toprak kapasitelerini gündeme getirmiş ve her iki transformatör içinde başlangıç aşırı gerilim dağılımları incelenmiştir.
Özet (Çeviri)
SUMMARY AMORPHOUS ALLOY CORE DISTRIBUTION TRANSFORMERS The basic aim of this work is to identify and critically assess the physical properties of commercially available amorphous alloys and to examine their potential as soft magnetic core material for distribution transformers. However, for this research, the characteristics of amorphous alloys which show potential for use in transformer cores are examined in comparison with the properties of the conventional material. Both an amorphous and a conventional transformer are designed and the results of this work is discussed. As it is known, distrubition transformers are one of the most fundemental parts of the transmission and distribution power systems. Theory and design problems of amorphous core transformers are given below. AMORPHOUS MATERIAL FOR TRANSFORMER CORES Amorphous metals, metallic glasses, glassy metals and a variety of trade names from several manufacturers are all terms which have appeared in recent technical literature. All these terms are inter-changeable and simply mean a metal alloy with a non-criystalline atomic structure. These non-crystalline solids are created by the rapid quenching of metal-metalloid alloys. The required quench rate of approximately one million degrees centigrade per second is achieved by ejecting the molten metal from a slotted nozzle onto a rapidly moving cooled substrate. This process produces a continous strip about 0.025 mm thick at a speed of more than 25m/s. The most important properties of amorphous alloys are their exceptional soft magnetic properties and the potential for low production cost. However, they have several deficiencies when being considered for application in transformers. First they have a low magnetic saturation density of approximately 1.57 T with M5 silicon steel which saturates at about 2.0 T. A second deficiency is the very thin gauge (approx. 0.025 mm) compared with conventional core material. The thin gauge means that more material must be handled, increasing the product manufacturing cost. The thin gauge combined with a less uniform surface finish leads to a lower core stacking factor. Furthermore, the low stacking factor combined with the low magnetic saturation means that larger cores must be used. This will affect the volume of conductor required in the device and hence the copper loss. Amorphous metals are also harder, and when annealed are more brittle than conventional materials. Due to the extreme hardness of amorphous metals, conventional shear cutting and slitting tools have an unacceptably short VIlife. Cutting tools have been dulled to the point of being in effective after less than 10% of the normal life observed when cutting conventional materials. It is the low core loss and excitation current performance (at acceptable induction levels) that make amorphous alloys strong candidates for application in electromagnetic devices. At 50 Hz a general purpose amorphous alloys in its“as cast”state is superior to silicon steel M5 annealed laminations in both core losses and excitation up to 1,4 T. NEED FOR REDUCTION OF CORE LOSSES Concern has been felt for the core losses occuring in distribution transformers since these are present even when the transformer is under no- load conditions. In rural areas, the load factor is very low due to peculiar conditions of most power being required for pump-sets etc. for a few hours during farming. However the distribution transformers have to be kept energized all the time. Under these conditions it has been felt necessary to reduced core losses. THE STRUCTURE OF AMORPHOUS ALLOYS CORE Amorphous alloy has thickness of 25 ^im and is available in widths up to 200 mm. The high resistivity (1,3 nQm compared with 0,48 p.Qm for M5 silicon steel) reduced thickness, absence of magnetic anisotropy and aligned domain structure all limit both hysteresis and Foucault current loss components to a minimum loss of 0,18 W/kg at 1,3 T, 50 Hz Developments to date have overcome several disadvantages associated with alloy characteristics. The alloy is very hard and flexible, making handling and cutting difficult, while losses are highly sensitive to mechanical stress. Amorphous alloy cores are extremely sensitive to compressive stresses. The core loss and excitation power respectively of the amorphous alloy core increase with clamping pressure. The frame and clamps used in the amorphous alloy transformer must be more substantial than those used in the traditional design. Traditional methods of core-to-winding packing may not be used as these would introduce high local stresses The windings must then be placed in a separate frame capable of withstanding forces generated in a short circuit fault condition. The changes are necessary because of the high stress sensitivity of iron loss and excitation power in the amorphous material. Excessive compressive stresses must be avoided in the stack direction and minimised across the strip width. Small tensile stresses along the axis of the strip may be beneficial. CORE LOSS MECHANİSMS In the third chapter of this work, it is studied the alloy core loss. The total core losses are obtained from two major components, referred to as the Vllhysteresis end Foucault current components have linear and quadratic dependences on the magnetizing frequency. The Foucault current component, itself, is separable into two parts, traditionally referred to as the classical and excess Foucault current components. The classical component refers to the rate of magnetization change in a uniformly magnetized material, and does not acknowledge the existence of ferromagnetic domains. The excess Foucault current losses are a direct consequence of the presence of domains and arise from currents localized at the domain walls. Simple magnetic structures, termed domains are associated with the grain orientation and consist of adjacent inter-grain volumes magnetized to saturation in opposite directions and separated by 180° domain walls which are thin planar regions across which the magnetization reverses through 180°. The simplicity and alignment of the magnetic domains, both within and over grains, dictates superior magnetic properties and low energy loss. An increase in the number of domain walls available to move and action the magnetization process, reduced their overall velocity and thus minimizes f2 loss. The/ loss, which relates mainly to the excess Foucault currents induced in the steel by the motion of domain walls during the magnetisation process, is also reduced by increasing material resistivity and decreasing strip thickness. Perfection of grain orientation, grain size, thickness, surface topography, metallurgical purity and mechanical stress in the steel (resulting from surface coating and externall forces) all contribute to modify the domain structure and its response to alternative current magnetization. The first three factors are critical for loss minimization. SURGE VOLTAGES IN TRANSFORMER WINDING It has been said to core were extremely sensitive to compressive stresses. Therefore, it should be avoided supporting the coils on the core and supported the coil with the frame which is named insulation tube. In the fourth and fifth chapter of this work, amorphous core and M5 silicon steel core transformer have been designed and then end of these section the surge voltages distributions for each one have been calculated. Transformer primary windings may be subjected to the sudden impact of high-fraquency waves arising from switching in operations, atmospheric lighting discharge, arcing grounds and short circuits, and, in fact, from almost any change in the electrostatic and electromagnetic conditions of the circuits involved. The failures which occured on the line end coils have been to the concentration of voltage arising on those coils as a result of the relative values and distribution of the inductance and of capacitance between the turns of the coils. VUlWhen the windings are subjected to the sudden impact of high-voltage and high-frequency or steep-fronted waves, the effect of electrostatic capacitances in determining the intial voltage distribution become important. The effects in transformers having an earthed and an isolated neutral are illiustrated for the two cases of an uninterrupted surge wave and an interrupted wave. It will be noted that, with both types of surges, the internal winding surge voltages to earth are more severe when the neutral is isolated. The initial distribution of voltage is not uniform owing to the fact that there is appreciable capacitance between the windings and the core in addition to the interturn capacitances, and neglecting inductance. But the distribution of inductance in a transformer is pratically uniform and, therefore, the final distribution of voltage also is uniform. If the paraleli capacitances of the windings to earth is minimized and the series capacitance of the windings which is between layers maximized, initial voltage distribition brings near the final voltage distribution. CT = The paraleli capacitance of the winding to earth Cs = The series capacitance of the winding As a result, if the initial voltage distribution equals to the final voltage distribution which is the linear, surge voltage disperses into the all coils as balance. AMORPHOUS ALLOY CORE MATERIAL vs CONVENTIONAL SILICON STEEL CORE The technical data of amorphous alloy core and M5 silicon steel transformers is given, as follows; -Rated power: 250 kVA -Rated primary voltage: 10000±5% Volt -Rated secondary voltage: 400 Volt -Frequency: 50 Hz -Installing condition: Outdoor -Connected group: Dyn5 (Triangle-star-output neutral) -Type: Oil-immersed -Type of cooling: Natural cooling For both of these sample transformers, P0, P& uk, at and axial, radial forces values and these dimensions are calculated and given in Tablo I and II. IXTABLO TABLO II The main merits and damerits of amorphous alloy core material as compared to the conventional silicon steel core are discussed in the work. The amorphous alloy core material has 0.18 Watt/kg (1.3 T,50 Hz) against 0.89 Watt/kg (1.5 T,50 Hz)of conventional M5 silicon steel core. This positive consideration itself outweighs the other disadvantages of the amorphous alloy. The excitation current in amorphous alloy core transformers is less by over 80% than that in transformers with M5 silicon steel core. The amorphous alloy is produced as a one-step process against multiple steps in producing M5 silicon steel. The amorphous alloy saturates at 1.57 Tesla whereas the M5 silicon steel saturates at around 2.0 Tesla. Thus amorphous alloy core transformers result in increase in core size, coil(conductor material), tank size and insulating oil. Magnetic core of transformer using M5 silicon steel core is built by stacking punched lamination whereas for amorphous alloys it is very difficult to make laminations due to hardness, brittleness and less thickness. M5 silicon steel is rolled into its final thickness while amorphous alloy is usually cast ino its final form. This creates surface roughness and thickness variation in the amorphous alloy core and consequently results in lower stacking factor of about 80% against 95-97% in M5 silicon steel.
Benzer Tezler
- Çekirdeği amorphous alaşımlı transformatörlerle çekirdeği silisyum saclı transformatörlerin karşılaştırılması
The Comparison of transformers with amorphous metal alloy core and those with silicon metal sheet core
FUAT BÜYÜKTÜMTÜRK
Doktora
Türkçe
2000
Elektrik ve Elektronik MühendisliğiMarmara ÜniversitesiElektrik Eğitimi Ana Bilim Dalı
Y.DOÇ.DR. FEVZİ KENTLİ
- Transformatör çekirdeklerinde kullanılan elektrik çelikleri ve amorf şeritlerin uç uca gelen birleşim yerlerindeki manyetik akı dağılımının deneysel ve kuramsal incelenmesi
Theoretical and experimental investigation of magnetic flux density distribution at joints of stacked electrical steels and amorphous ribbons used transformer cores
SEZER ERDEM
Doktora
Türkçe
2006
Elektrik ve Elektronik MühendisliğiUludağ ÜniversitesiFizik Ana Bilim Dalı
PROF. DR. NAİM DEREBAŞI
- Amorf çekirdekli 33/0.4 kV 1MVA dağıtım transformatörü tasarımı ve performans analizi
Amorphous core 33/0.4 kV 1MVA distribution transformer design and performance analysis
FATİH IŞIK
Doktora
Türkçe
2014
Elektrik ve Elektronik MühendisliğiSakarya ÜniversitesiElektrik-Elektronik Mühendisliği Ana Bilim Dalı
DOÇ. DR. YILMAZ UYAROĞLU
- Güç transformatörlerinde çekirdek kayıplarının silisli çelik ve amorf malzeme için karşılaştırılması
A Comperative study of power transformer core losses using silicon-iron cores and amorphous cores
ERCAN ÖKSÜZ
Yüksek Lisans
Türkçe
2000
Elektrik ve Elektronik MühendisliğiHacettepe ÜniversitesiElektrik-Elektronik Mühendisliği Ana Bilim Dalı
PROF. DR. BAHRİ ERCAN
- Enerji sistemlerinde kullanılan gerilim transformatörlerinde farklı çekirdek yapılarının analizi
Different core structure analysis of voltage transformers used in the power systems
MUSTAFA CANER AKÜNER
Doktora
Türkçe
1999
Elektrik ve Elektronik MühendisliğiMarmara ÜniversitesiElektrik Eğitimi Ana Bilim Dalı
PROF.DR. İRFAN GÜNEY