Simulacija in optimizacija asinhronskega stroja s kratkostično kletko

GRABNAR, BORIS (author), Miljavec, Damijan (mentor)

V magistrskem delu je prikazan razvoj programske opreme za simulacijo in optimizacijo asinhronskega stroja s kratkostično kletko. Simulacija je izvedena v domeni končnih elementov z že obstoječim programom za simulacijo struktur v domeni končnih elementov (FEMM). Prikazana je tudi uporaba izdelanega programa na primeru že obstoječega oz. v industriji izdelanega stroja. V drugem poglavju so najprej predstavljene osnovne značilnosti uporabljenih programskih orodij (Microsoft Visual Basic, FEMM, Scilab). Jedro magistrskega dela je v tretjem poglavju in predstavlja razvoj programa, ki je smiselno razdeljen na več samostojnih modulov. V začetnem delu je prikazan razvoj grafičnega vmesnika za parametričen vnos konstrukcijskih podatkov stroja, ki so osnova simulacije. Grafični vmesnik je razvit z okoljem Microsoft Visual Basic in predstavlja interaktivno povezavo med uporabnikom in vsemi moduli programa. Ko so konstrukcijski podatki stroja znani, se lahko izdela model stroja v programu FEMM. Pri tem se moramo zavedati, da je model stroja dvodimenzionalen in tako zanemari številne pojave. Iz danega razloga je v nadaljevanju programa izvedena še dopolnitev modela stroja, ki deloma upošteva zanemarjene pojave (kot povišana specifična upornost se upoštevajo glave statorskega navitja, kratkostični obroč, delovna temperatura navitja in faktor polnjenja navitja v utorih). Ko je model stroja v programu FEMM dopolnjen, se lahko izvede simulacija stroja. V programu FEMM je predpostavljeno, da so vsi modeli tokovno napajani. V mojem primeru želim imeti napetostno napajan stroj, zato je treba v program vključiti določeno iteracijsko metodo (postopno približevanje), ki poišče ustrezen tok za doseg želene napetosti na navitjih. Ker je model stroja dvodimenzionalen, je v izračun naknadno vključeno tudi stresanje glav navitja in kratkostičnega obroča, ki ju izračunamo analitično. V simulaciji so izgube v jedru stroja zanemarjene, le-te se izračunajo na podlagi rezultatov poprocesorja programa FEMM. Vsi bistveni podatki, pridobljeni s simulacijo, se shranijo v posebno tekstovno datoteko in so tako na voljo za nadaljnjo analizo. Na podlagi shranjenih podatkov simulacije je v nadaljevanju prikazan način izračuna elementov nadomestnega vezja v odvisnosti od slipa, izveden pa je tudi izračun karakteristik stroja na podlagi nadomestnega vezja. V zadnjem delu je v program vključena še optimizacija geometrije stroja, ki temelji na metodi oblikovanja poskusov (ang. Design of experiments). V program sta vključeni dve metodi oblikovanja poskusov, in sicer metoda Taguchi ter metoda centralno kompozitno oblikovanje (ang. Central composite design). V kombinaciji s centralnim kompozitnim oblikovanjem je uporabljena še metodologija odzivnih površin (ang. Response surface methodology) in optimizacija z genetskimi algoritmi. Magistrsko delo smiselno zaključuje četrto poglavje, kjer je prikazana uporaba programa na že obstoječem oz. izdelanem stroju. Najprej je izvedena simulacija izbranega stroja v programu FEMM ter primerjava rezultatov simulacije z rezultati meritev stroja v laboratoriju. Izkaže se, da izdelan program zadovoljivo modelira in analizira asinhronski stroj za potrebe magistrskega dela. Slednja ugotovitev je pomembna, saj je na danem modelu izvedena še optimizacija geometrije stroja za konkreten primer iz industrije (čim višji izkoristek pri nazivni moči stroja), in samo če je model stroja ustrezen, lahko pričakujemo verodostojne rezultate. Pri prvem poskusu optimizacije je narejena samo optimizacija za čim višji izkoristek pri nazivni moči stroja, pri čemer nam cena stroja in ostale količine niso pomembne. V tem primeru se je izkazalo, da je možno precej izboljšati izkoristek stroja (izkoristek se poviša za 2,9 %), vendar pa se pri tem neizbežno povečajo dimenzije stroja in s tem cena izdelave (cena se poviša za 16 %). Precej se zniža tudi faktor delavnosti. V drugem primeru imamo poleg obstoječih zahtev še zahtevo po čim nižji ceni in čim višjemu faktorju delavnosti, zato se izkoristek stroja ne poveča izjemno veliko (za 1,4 %), cena stroja pa se poviša za 12,6 %. Faktor delavnosti pa je v tem primeru višji (glede na referenčni stroj).

• Language: Slovenian
• Keywords: asinhronski stroj, simulacija, metoda končnih elementov, FEMM, Scilab, optimizacija, metode oblikovanja poskusov, centralno kompozitno oblikovanje, metodologija odzivnih površin, genetski algoritem.
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2015
• PID: 20.500.12556/RUL-72492
• Publication date in RUL: 24.09.2015

Secondary language

• Language: English
• Title: Simulation and optimization of induction machine with squirrel cage

Abstract

In this master thesis a development of software for simulation and optimisation of a squirrel cage induction machine is shown. The simulation itself is based on a finite element method software FEMM. An example of using created software on a machine, that has already been built, is also presented. In its core the software accesses other, already developed software, where each contributes to the final design and experience and for this reason there is a basic description of this programs presented in chapter 2. The core of master thesis is presented in chapter 3, where the development of this program, that consists of many modules, is described in detail. In the initial part the development of graphical user interface (GUI) for parametrical input of machine construction data is shown (whole simulation is based on this parameters). The GUI itself is developed with the help of Microsoft Visual Basic (Express edition) and in general presents interactive connection between the user and all the modules of the software. Once the software has construction parameters in the memory, we can perform an automatic machine construction in an externally used software FEMM (runs in the background). At this point we have to be aware that the machine model is two dimensional and therefore does not comprise all the phenomena that is present in the real machine. For this reason there is a special module intended to partially include extra effects in the model. For example, winding head, short circuit ring, working winding temperature, winding fill factor, etc. are all included in the model as raised specific resistivity of the material. Once the model is adequate, machine simulation can be performed. In FEMM it is assumed that all models are current fed, whereat in my case I want the model to be voltage fed, so special iterative method (successive approximation) is used to ensure the desired phase winding voltages. Because the model is two dimensional, winding heads leakage and short circuit ring leakage are analytically calculated and subsequently included in the model. Core losses are neglected in the simulation, they are calculated based on the FEMM postprocessor results. Data that we collect during simulation is automatically stored in a text file, for possible further analysis with the help of Scilab. Based on the data, collected from simulation, the software can calculate and graphically show the equivalent circuit elements in function of slip and all essential characteristics of the machine. In the last part a simple geometry optimisation of an induction machine is implemented. Optimisation is based on design of experiments. There are two methods of design of experiments, programmed into this software, namely the Taguchi method and central composite design (CCD). In combination with CCD the response surface methodology (RSM) and genetic algorithm based optimisation are also used. Master thesis is logically concluded with the fourth chapter, where practical use of this software on already developed machine is presented. The simulation of the existing machine is first performed in FEMM. Then comparison of results between simulation and real laboratory measurement is done and it turns out that produced software sufficiently models and analyzes presented induction machine. This finding is necessary, because there is also an optimisation done on this model and we can expect reliable result, only if the machine model is suitable. In the first optimisation attempt, the optimisation goal is maximum efficiency at nominal output power where price of the machine and other objectives are not important. In this case it turned out, that it is possible to increase the efficiency for quite a lot (in my experiment for 2,9 %), but there is also a inevitable increase in mass of the machine and consequently in price (price is increased by 16 %). There is also a decrease in power factor. In the second optimisation attempt also price (minimum) and power factor (maximum) were taken into consideration. In this case efficiency of the machine is not so greatly improved (only for 1,4 %), but on the other hand there is lower increase in price (12,6 %) and better power factor as in the first case.

• Keywords: induction machine, simulation, finite element method, FEMM, Scilab, optimisation, design of experiments, central composite design, response surface methodology, genetic algorithm.