STUDY OF INDUCTION MACHINE UNDER TRANSIENT DUTY AND STEADY-STATE AS SYNCHRONIZED MACHINE

Autor/autori: Prof. Eng. Alecsandru Simion, PhD, Assoc. Prof. Eng. Leonard Livadaru, PhD, Assist. Prof. Eng. Adrian Munteanu, PhD

Rezumat: In vederea analizei masinii asincrone trifazate in regim de masina sincrona (masina asincrona sincronizata MAS) se apeleaza la ecuatiile diferentiale de ordinul I exprimate numai in fluxuri totale si unghiul de rotatie. Se obtine un sistem de 8 ecuatii care se refera: la cele 3 faze statorice, la cele 3 faze rotorice, (dintre care 2 sunt inseriate si sunt alimentate de la o sursa de curent continuu, constituind infasurarea de excitatie, iar cea de-a treia constituie infasurarea de amortizare, fiind conectata in scurtcircuit), la care se mai adauga 2 ecuatii de miscare. Aceasta abordare permite obtinerea unor informatii directe-precise despre fenomenele care au loc in masina, inclusiv si despre directiile de actiune ale fluxurilor magnetice adica despre unghiul intern instantaneu. Pe baza acestor informatii se pot adopta strategii adecvate si lua decizii pertinente privind momentele favorabile ale cuplarii infasurarilor la surse. Trebuie evitata situatia de decrosare, de exemplu, cand se declanseaza un regim tranzitoriu electromecanic cu constanta de timp mare, care intarzie procesul cu o durata care poate fi egala cu dublul timpului necesar pornirii. Se insista asupra utilizarii hodografului fluxului rezultant rotoric ca instrument eficient, cu reale valente didactice in aprecierea comportarii masinii de inductie sincronizate in diverse regimuri: tranzitorii sau stationare.

Cuvinte cheie: motor asincron de putere mare, conditii de pornire speciale, doua colivii rotorice, simulare MEF


Abstract: For the analysis of the three-phase induction machine under synchronous operation (the so-called synchronized induction machine, SIM) one uses first order differential equations that contains nothing but total fluxes and rotation angle. The resulted 8 equations system characterize the 3 stator phases, the 3 rotor phases (2 of them are series connected and fed from a DC source and the third is short-circuited and play the role of a damper winding) and the movement of the rotor (the last 2 equations). This approach allows the obtaining of direct and proper information about the intimate phenomena that take place inside the machine including the direction of magnetic fluxes, which leads to the instantaneous internal angle. On the basis of this information, one can adopt proper strategies concerning the most favourable moment for the connection of the windings to the supply sources. The pulling out must be avoided, for example when starts a transient duty with high time constant which delays the process with a length that may attain twice the value of the starting time. The hodograph of the resultant rotor flux is considered as a very effective tool, also for didactic purpose, that describe the behavior of the synchronized induction machine under different duties such as transients or steady state.

Keywords: high power induction motor, start-up constraints, two squirrel cages of distinct materials, FEM simulation

 

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