Low-voltage synchronous generator excitation optimization and design

Tahtigeneraattorit suunnitellaan asiakkaiden tarpeiden mukaisesti. Automaattinen suunnittelu ja standardoidut ratkaisut ovat välttämättömiä generaattoreiden modifioimiseksi eri asiakkaille ja erilaisiin sovelluksiin sekä tilaus-tarjousprosessin nopeuttamiseksi. Tässä työssä suunnitellaan matalajännitteisen tahtigeneraattorin magnetointijärjestelmä. Magnetointi toteutetaan apukäämillä, joka käyttää ilmavälivuontiheyden yliaaltojen tehoa automaattisen jännitteensäätäjän syöttämiseksi. Työssä luodaan standardoitu ratkaisu apukäämille ja jännitteensäätöjärjestelmälle. Työssä tutkitaan erilaisia apukäämiratkaisuja ja valitaan optimaalinen ratkaisu matalajännitteiselle tahtigeneraattorille. Valitun apukäämiratkaisun analyyttinen mitoitus toteutetaan tietokoneohjelmana. Eri standardien ja luokituslaitosten magnetoinnille asettamia vaatimuksia tutkitaan. Myös apukäämillä syötetyn automaattisen jännitteensäätäjän vaatimuksia pohditaan, ja jännitteensäätöjärjestelmälle luodaan ratkaisu. Tämä diplomityö kuvaa matalajännitteiseen tahtigeneraattoriin valitun magnetointiratkaisun. Työssä esitetään apukäämiratkaisu, apukäämin mitoitusprosessi sekä automaattinen jännitteensäätöjärjestelmä. Työssä valittiin apukäämiratkaisu, jossa magnetointiteho otetaan ilmavälivuontiheyden perusaallosta sekä kolmannesta yliaallosta. Perusaaltoa käytetään tyhjäkäynnissä ja kuormituksessa ja kolmatta yliaaltoa oikosulussa. Tämä toteutetaan kahdella eri käämillä, jotka mitoitetaan erikseen oikosulku- ja kuormitustilannetta varten. Apukäämimagnetoinnin käyttäminen matalajännitteisissä tahtigeneraattoreissa yksinkertaistaa automaattista jännitteensäätäjäratkaisua. Kahta eri syöttötaajuutta käytettäessä käytettävän säätäjän tulee toimia katkojaperiaatteella tyristoritasasuuntaajan sijaan.Synchronous generators are designed to match the customers' needs. Automated design and standardized solutions are necessary to simplify the modification of the generators for different customers and applications and to speed up the inquiry-offer process. In this work, a solution for the excitation system of a low-voltage synchronous generator is designed. The excitation system is implemented with an auxiliary winding utilizing the power in air-gap flux-density harmonics to supply the automatic voltage regulator. A standard solution for the auxiliary winding and the voltage regulator system is created. Different auxiliary winding solutions are studied and the optimal solution for the low-voltage synchronous generators is selected. The analytic dimensioning of the selected auxiliary winding solution is implemented as a computer program. Requirements set for the excitation by different standards and classification societies are studied. The requirements for the auxiliary-winding supplied automatic voltage regulator are discussed and a solution for the voltage regulator system is implemented. This thesis describes the selected solution for the low-voltage synchronous generator excitation system. The auxiliary winding solution, dimensioning process of the auxiliary winding and the automatic voltage regulator system are presented. The selected auxiliary winding solution utilizes the air-gap flux-density fundamental and third harmonic component to supply the excitation power. The fundamental is used in no-load and load operation and the third-harmonic component in generator short circuit. This is implemented with two different windings dimensioned independently for the on-load and short-circuit operation. Using auxiliary-winding supplied excitation in low-voltage synchronous generators reduces the complexity of the automatic voltage regulator solution. Since two different supply frequencies are used, the operation of the regulator has to be based on a direct-current chopper converter instead of a thyristor bridge converter

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