Çıkık kutuplu orta güçlü senkron generatörlerinin ana boyut ve magnetik devre hesabı için nümerik algoritma

Abstract

Bu tezde, çıkık kutuplu senkron generatörlerin ana boyut ve magnetik devre hesaplarının bilgisayar programı desteğinde yapılması amacıyla literatür kriterleri göz önünde bulundurularak bir algoritm geliştirilmiştir. Bu çalışma neticesinde elde edilen sayısal sonuçlar ve mıknatıslanma karakteristikleri, literatürde daha önce klasik yolla elde edilen sonuçlarla karşılaştırılarak, algoritmin geçerli olduğu parametre bölgesi ve doğruluk derecesi irdelenmiştir. Tezin ilk bölümünde, geliştirilen bilgisayar programının teknik özellikleri ve yapısı hakkında temel bilgiler verilmiştir. İkinci bölümde, senkron makinalara ait kısa genel bilginin yanında, bilgisayar programının oluşturulmasında dikkate alınan çıkık kutuplu senkron generatörlerin temel hesap kriterlerine yer verilmiştir. Üçüncü bölümde, programın mantığı işlem blokları bazında detaylı bir şekilde ele alınmış ve ayrıca program akış diyagramı verilmiştir. Dördüncü bölümde programın bir uygulama örneği yapılmış, elde edilen sonuçlar, literatürde daha önce bulunmuş olan sonuçlarla karşılaştırılarak, programın geçerlilik derecesi ve performansı irdelenmiştir.

Engineering and scientific software has been characterized by "number crunching" algorithms. Applications range from astronomy to volcanology, from automotive stress analysis to space shuttle orbital dynamics and from automated manufacturing to system designing. With this manner, we interested, in calculation of main dimension and magnetic circuits of salient-pole synchronous generators by a numerical algorithm for specifying basic design parameters of salient-pole synchronous generators, which is a part of the electrical machine industry. Although new applications within the engineering/scientific area are moving away from conventional numerical algorithm and computer-aided design (CAD) system simulation and other interactive applications have begun to take on real time, the numerical analysis, which constitudes a step to these modern applications, still keeps its importance at system design area. In explaining procedure in design an attempt has been made to base all arguments an scientific facts and to build up a design in a logical manner from known fundamental principles. This admittedly different from the method followed by the practical designer, who uses empirical formulas and "short cuts" justified only by experience and practical knowledge. As known, engineering is the economical application of science to time and material ends, and the engineer must always have in mind the question of cost, not only material, labor cost which depends on the size and complication of parts, accessibility of screws and bolts, and similiar factors, but also the time. An affort is made to keep the algorithm as simple as possible without making unreasonable or unpractical assumptions which would seriously effect the accuracy of the calculated results. Sine- wave forms are assumed, and all higher harmonics are neglected. Here we present a numerical algorithm of salient-pole, synchronous generator calculation and compare results with the results determined by conventional method in the literature. In section 1 we introduce the problem and outline scope of this work. The software according to calculation of main dimension and magnetic circuits of salient-pole synchronous generators, is codded by PASCAL programming language. As known Pascal is a modern programming language developed in the early 1970's for teaching modern techniques in software development. Since its -xii- introduction, Pascal has found growing support from a board audience of software developers and is used widely for engineering/scientific applications and system programming (the language has been called "the FORTRAN of the 1980s") [1]. That's why PASCAL is used for codding this algorithm. Also, at output of this algorithm its benefited from MATLAB programme having a capability to draw graphics. Figure 1 shows process block schematic of the programme. Enter ing by user PASCAL Processing of input datas Drawing parameters of the magnetization curves MATLAB Processing of input datas 1 calculated values main dimensions and magnetic circuit magn i tudes Magnet i z i ng curves Figure 1. Process block schematic of the programme. As shown in the block schematic, PASCAL, including the main programme is used for processing of input datas entered by user and MATLAB is used for graphical drawings of magnetizing curves by using the parameters, produced by the main programme. The algorithm is divided to a number of individual PROCEDURES, including the main concepts, according to calculation of synchronous generators to ensure the possibility for developing individually. These concepts are as follows: - Stator - Rotor - Magnetic circuits - Reactance - Phasor diagram - Excitation - Losses -Xlll- As known, with rare exceptions, the armature winding of a synchronous generator is on the stator. The field winding is on the rotor, with the field current conducted to it through carbon brushes bearing on slip rings or collector rings. Preliminary ideas of AC generator action can be gained by discussing the elementary AC generator of Fig 2. Armature structure or stator Armature winding Field winding. Excited by direct current through slip rings Field pole produced by direct current in field winding Field structure or rotor Fig. 2. Elemantary three phase two pole synchronous generator. On the armature of this three-phase two-pole generator are three coils, aa', bb' and cc', whose axes are displaced 120° in space from one another. The field winding is excited by direct current. The rotor is turned at a constant speed by a source of mechanical power connected to its shaft. The machine is normally so designed that the distribution of flux around the air gap circumference is a sine wave. It is well to distinguish between two classes of alternators: 1. Machines with salient poles, driven at moderate speeds by belt or direct- connected to reciprocating steam, gas, or oil engines, or to water turbines. The peripheral speed of the rotating part will be generally up to 80 m/sec [2]. 2. Machines direct-coupled to high-speed steam turbines in which the peripheral velocity will be usually up to 200 m/sec [2]. The peripheral speed of a synchronous generator is calculated from, it.D n" v_=- 60 [m/sec] (1) where Dr is diameter of armature in meters and ns is revolutions per minute. -xiv- The algorithm is based on basic design criteria of salient-pole synchronors generators. Some of these basic assumptions considering in section two, are specified below: Ll 0.7 s - <; 2.5 xp Where Lj is length of stator in [cm] and t is pole pitch in [cm] 0.01 * - <; 0.02 where 50 is air-gap at center of pole shoe in [cm] 2 * x0 * 7 where xg is slot pitch in [cm] 3 <; s" <; 5 where ^a is current density in armature conductors in [A/mm2] 1.6 * Bj. $ 1.9 where Bdi is magnetic induction at top of teeth in [tesla] 3 s -2 s 6 where hQ is slot depth in [cm] and b0 is slot width in [cm]. 1.2 s Bp i 1.5 where B is magnetic induction at pole 3 <, s.,s_ s 4.5 mn* tntnox where smn is current density at nominal excition current [A/mnrr] and smmax is current density at maximum excitation current [A/mm2] In section three, logic of the algorithm is discussed procedure by procedure and also flow chart is given in this section.