Transformatörlerde pencere boyutlarının eşdeğer devre parametreleri ve kuvvetler üzerine etkileri
Başlık çevirisi mevcut değil.
- Tez No: 55635
- Danışmanlar: PROF.DR. NURDAN GÜZELBEYOĞLU
- Tez Türü: Yüksek Lisans
- Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 54
Özet
ÖZET Bu çalışmada, çekirdek tipi transformatörlerde pencere boyutlarının, eşdeğer devre parametrelerine ve elektrodinamik kuvvetlere olan etkisi incelenmiştir. Bunun için hesabı yapılmış alçak gerilim, üç fazlı kendi kendine hava ile soğumalı kuru tip bir transformatörde, pencere yüksekliği ve genişliği değiştirilerek yedi model tasarlanmıştır. Bu yedi modeldeki aksiyal ve radyal kuvvetler E.Roth metodu ile hesaplanmıştır. Normal çalışma koşullarında, transformatörlere etki eden kuvvetler müsaade edilir sınırlar içindedir. Ani bir kısadevre halinde bu kuvvetler çok büyük değerlere ulaşabilir. Bu kuvvetler kısadevre akımının karesi ile orantılıdır. Bu tez çalışmasında, çekirdek pencere yüksekliği arttıkça bağıl anma kısadevre geriliminin azaldığı, dolayısıyla anma kısadevre akımının ve darbe kısadevre akımının arttığı belirlenmiştir.
Özet (Çeviri)
SUMMARY THE EFFECTS OF WINDOW DIMENSIONS ON IDENTICAL CIRCUIT PARAMETERS AND FORCES IN TRANSFORMERS The basic aim of this work is to observe forces with changing core window dimensions in core-form power transformers. However, for this research; low-voltage, three-phase, air-cooled dry type power transformers is chosen, and seven models are designed by changing window height and window width of core. Axial and radial forces are calculated by Roth's method. As it is known, power transformers are one of the most fundamental parts of the transmission and distribution power systems. Theory and design problems of the transformers are given below. Function of the Transformer and Transformer Theory The function of the transformer is to change electric power from one voltage to another. The use of transformers enables power to be generated at any convenient voltage, stepped up to an economical transmission voltage, and stepped down again at the end of the transmission line to the desired voltage for use. Practically all transformers are either single-phase transformers or three-phase transformers. Most transmission lines are three-phase, and these can be served either by three-phase transformers or by banks of single-phase transformers. Other multiphase circuits are sometimes required,e.g.,two-phase for certain motors,six-phase for most rotary converters,and twelve or more phases for large rectifiers,but they can all be derived from three-phase circuits by means of transformers. The fundamental fact about a transformer is that energy can be transferred from one winding to another winding on the same magnetic circuit by means of a varying magnetic flux. The winding which receives energy from an external source is called the primary winding,and that which receives energy from the primary by magnetic induction is called the secondary winding. A transformer may have one or more secondary windings. When an alternating voltage is impressed on the primary winding,a small current will flow. This is the exiting current which produces the magnetic flux in the magnetic circuit This flux.linking the turns of the primary winding.induces a voltage practically equal and opposite to the applied voltage. And the same flux Jinking the turns of the secondary VIwinding.induces the same volts per turn as in the primary. The ratio of primary to secondary volts.therefore,is the same as the ratio of primary to secondary turns. If a load is connected to the secondary winding,the induced secondary voltage will cause a current to flow. The ampere turns thus produced in the secondary winding must be balanced by equal and opposite ampere turns in the primary winding, The ratio of secondary-load amperes to primary-load amperes.therefore,is the same as the ratio of primary turns to secondary turns. From these relations of primary to secondary volts and amperes it follows that the primary kilovolt-ampere input is the same, neglecting losses,as the secondary kilovolt-ampere output. Any desired voltage may be obtained by means of a transformer of the proper ratio from any available voltage of the same frequency. Characteristics of Transformers Transformers apply Faraday's discovery by using two copper circuits linked with an iron circuit, The iron circuit is built up of thin plates of special steel, The two copper circuits may be entirely independent and insulated from each other, as in two-winding transformers, or they may have part of their turns in common, as in an autotransformer. When an alternating voltage is applied to the terminals of one of the copper circuits, an alternating current will flow which will magnetize the core first in one direction and then in the other. This induces a voltage in the second coil, and if lamps or other loads are connected to the terminals of the second coil, current will flow. The ratio of the primary to secondary volts is the same as the ratio of primary to secondary turns, and the ratio of the primary to the secondary amperes is the same as the ratio of secondary to primary turns. Design Problems When current flows in a transformer, heat is generated, both in the coils and in the core. Too much heat, however, is an enemy of insulation, and one of the designer's major problems is to prevent the transformer from reaching too high a temperature. Other major problems are to provide sufficient insulation and to arrange it so that the transformer will withstand any voltage condition which it may encounter in operation, to produce a transformer which will operate with satisfactorily low losses, and to keep the material used, ands consequently the cost, at a minimum. This array of requirements calls for the exercise of skill and ingenuity on the part of the designer, and in the effort to get the best solution many and various arrangements of cores and coils have been worked out. Each arrangement has certain advantages, and several typical schemes will be shown. All the arrangements fall within one or the other of two general classes, called, respectively, shell form and core form. VIITransformer Cooling Energy losses occur in all kinds of electrical apparatus. Transformers are no exception to the rule, although their losses are less in proportion than those of most other electrical machines. The energy losses appear as heat, and one of the problems of transformer design is to provide means for getting rid of the heat. The method used depends on the size of the transformer and on the condition under which it is to be operated. Transformers may also be classified with regard to their method of cooling. Dry-type transformers are designed for operation without oil. Small dry-type transformers may be mounted in end frames with the coils exposed, for indoor operation, or they may be provided with metal housings for protection. Such transformers are cooled by the natural circulation of air around their coils and core. In large and medium-sized dry-type transformers additional cooling is provided by air ducts through the winding. And in air-blast power transformers the winding and the core are provided with many ducts through which air is forced at high speed by a blower. Small low-voltage transformers generally operate without oil. In the smaller transformers of this class the coils are wound without ducts. This is possible because a small transformer has a surface that is large in comparison with its volume and the watts to be dissipated per square inch of surface are therefore small. Also, the heat has a short distance to travel to reach the surface, and the interior of the transformer is therefore not much hotter than the surface. Such transformers may or may not be enclosed in metal cases. Mechanical Force If two wires carrying current in the same direction are near together, the lines of force from one, in the space between the two wires, will cancel the lines of force from the other, and the resultant field will encircle both wires, and tend to draw them together. If the currents are in opposite directions, the fields are distorted and crowded in the space between the two wires, and the tendency is to force the wires apart. In a coil of many turns these forces are multiplied, and one of the problems of design is to provide means for supporting the forces thus caused. Forces in Transformers In transformers all coils which carry current in the same direction attract one another and coils which carry current in opposite directions repel one another. In other words, all primary coils attract one another; likewise all secondary coils. But primary coils repel secondary coils, and vice versa. These effects always exits when the transformer is operating, but under normal conditions the forces are relatively small. In case of short circuit, VIIIhowever, these forces may become great enough to wreck the transformer if the coils are not adequately supported. Supporting the Coils The method of support depends on the coil arrangement. The magnetic flux then will be distributed, pulling like coils together and pushing the low-voltage coils away from the high-voltage coils. If the coils are symmetrically arranged, the forces within the transformer will be balanced, except the forces acting on the two end coils. In transformers with concentric coils the force between the primary and secondary windings is radial. This force tends to make the outer coil assume a circular shape and then tends to stretch the wire so as to increase the diameter of the coil. At the same time the radial force tends to crush the inner coil against the core. Fortunately, it is easy to brace the inner coil against the core so that it can not be crushed, and the tensile strength of the wire in the outer coil is ample to stand the stress which can be applied to it. This form of construction would be ideal from the standpoint of security against distortion by short circuits if perfect accuracy in building and assembly could be assured. But if one coil is displaced axially from its correct position by even a small amount, a large axial force may result. If the electrical centers of the two coils were exactly opposite, in the same plane, the force between the two coils would be purely radial, but if one coil is shifted, as shown, an axial component is introduced. The axial force may become large under short-circuit conditions, and the coils must be designed and braced to withstand it. The question of suitable mechanical construction and adequate coil support is thus as important as any other question of design. In the first chapter of this work, a general view over problem and the steps that the work will follow is given. In the second chapter of this work, the following low-voltage, three phase power transformer is taken into account for research: - Rated power: 100 kVA - Rated primary voltage: 380V±%5 - Rated secondary voltage: 220 V - Frequency: 50 Hz - Installing condition: Indoor - Connected group: Dyn 1 1 ( Triangle-star-output neutral ) - Type: Dry - Type of cooling: Natural cooling For the sample power transformers, seven different core-type models are designed by changing dimensions of window of core. In this chapter, these seven different models are introduced one by one. IXIn the thirth chapter, E. Roth Method is presented. Axial and radial forces belonging to the models are calculated by program written in Qbase programming language by E. Roth Method, and were given in a table. The other differences among the models were considered, like leakage reactance, relative rated short-circuit voltage, weight of core and windings, iron and copper losses, efficiency, equivalent circuit parameters and Electrodynamics forces respectively. By using these output data belonging to the models, in order to reduce forces, the ideal core-form transformer was determined.
Benzer Tezler
- Düzlemsel transformatör kullanarak ileri yönlü dönüştürücü tasarımı
Designing a forward converter using planar transformer
HARUN KURAL
Yüksek Lisans
Türkçe
2024
Elektrik ve Elektronik Mühendisliğiİstanbul Teknik ÜniversitesiElektronik ve Haberleşme Mühendisliği Ana Bilim Dalı
DOÇ. DR. METİN YAZGI
- Üç fazlı transformatörler için yeni bir geçmeli tip çekirdek tasarımı
A new plug-in core design for three phase transformers
DOĞANCAN ÇELEN
Yüksek Lisans
Türkçe
2021
Elektrik ve Elektronik MühendisliğiYıldız Teknik ÜniversitesiElektrik Mühendisliği Ana Bilim Dalı
DR. ÖĞR. ÜYESİ SİBEL ZORLU PARTAL
- Dalgacık tabanlı transformatör koruma algoritması
Wavelet based transformer protection algorithm
ÇAĞRI KOCAMAN
Yüksek Lisans
Türkçe
2003
Elektrik ve Elektronik MühendisliğiOndokuz Mayıs ÜniversitesiElektrik Tesisleri Ana Bilim Dalı
YRD. DOÇ. DR. OKAN ÖZGÖNENEL
- Transformatörlerde sargı sıcaklık dağılımı matematiksel modelinin sonlu elemanlar yöntemi ile oluşturulmasının esasları
Başlık çevirisi yok
SİNAN SÜRÜL
Yüksek Lisans
Türkçe
1998
Elektrik ve Elektronik Mühendisliğiİstanbul Teknik ÜniversitesiElektrik Mühendisliği Ana Bilim Dalı
PROF. DR. NURDAN GÜZELBEYOĞLU
- Transformatörlerde kısmi boşalmanın ölçümü ve konumunun belirlenmesi için yeni bir yöntem geliştirilmesi
Developing a novel method for partial discharge measurement and location in transformers
KAAN GÜLNİHAR
Doktora
Türkçe
2017
Elektrik ve Elektronik Mühendisliğiİstanbul ÜniversitesiElektrik-Elektronik Mühendisliği Ana Bilim Dalı
PROF. DR. MUKDEN UĞUR