Glavni cilj završnoga rada je odrediti nadomjesne sheme sinkronih strojeva te transformatora i obraditi per-unit metodu. Navedene su formule i načini rješavanja i računanja vrijednosti pojedinih elemenata koji su nam potrebni, sve u odnosu na sheme. Na temelju faznih dijagrama te modela opisane su najčešće korištene nadomijesne sheme sinkronog generatora i dvonamotnog, tronamotnog transformatora i autotransformatora. Uz njih, obraĎena je metoda jediničnih vrijednosti (per-unit metoda) koja pomaţe u proračunu elektroenergetskih mreţa s više naponskih razina. Dobivene nadomjesne sheme sluţe kao pomoć za rješavanje problema u zadatku. Pomoću njih se bolje vide elementi spoja, oni zadani i oni traţeni. Rad je namjenjen razradi tih shema radi pojašnjavanja i obrazloţavanja korištenja istih.

The aim of this paper is to determine the equivalent circuit of synchronous machines and transformers and to explain per-unit method. Formulas and ways of solving and calculating the value of the individual elements, in corellation with equivalent circuits, are shown in the paper. Based on the phase diagrams and models, the most commonly used equivalent circuits of the synchronous generator and dual winding, triple winding transformer and autotransformer are described. Along with them, the per-unit method is shown which helps in the calculation of higher-voltage power grids. Equivalent circuits are used to help solve the problem in the task. They can help in seeing the elements of the circuit, the given ones and the ones that must be calculated. The paper is intended to elaborate these schemes to clarify and explain their use.