U završnom radu opisan je princip rada električnog transformatora, utjecaj hlađenja na rad energetskog transformatora, U opisu rada transformatora naveden je osnovni princip rada, razmatranje idealnog transformatora, razmatranje realnog transformatora, postavljanje II Kirchhoff-ovog zakona za transformator te je prikazan utjecaj broja namota i glavnog magnetskog toka na inducirani napona sekundara, pogonska stanja transformatora - kratki spoj i prazan hod, načini spajanja namota trofaznih transformatora te grupe spoja namota i objašnjenje satnog broja te međusobno pomicanje namota transformatora za određeni kut. U drugom dijelu završnog rada opisano je hlađenje transformatora te je opisan utjecaj hlađenja na poboljšanje rada transformatora te smanjenje gubitaka prilikom većih opterećenja. Izrađen je i proračun energetskih gubitaka u transformatoru za različite razine opterećenja, te su grafički prikazani gubitci transformatora različitih snaga.

In this final paper there are several working principles explained regarding the electric transformer, which include how does the cooling system affect the output of the energy transformer. The main description explains the basic operation of the electric transformer, consideration of the ideal and realistic transformer, declaration of the II. Kirchhoff’s Law for the transformer and explaining the theory on how does the number of windings and main magnetic flux affect the induced voltage of the secondary coil, operating stages of the transformer - short circuit and no-load operation, methods for connecting coils of the three-phase transformer, coil connection groups, clock notation, and the mutual dislocation of the coils at a specific angle. The second part explains the cooling operation of the transformer, and how the cooling operation can improve the output of the transformer and reduce energy outage while operating on higher loads. A calculation has been made for calculating these energy losses in the transformer while operating on several different levels of loads. Power losses of transformers of various powers have been graphically shown.