In the final work, it is described in detail what is the transformer, and the physical appearance that occur during his work. Vector illustrations of alternating electrical quantities were used. Appropriate formulas and schemes were used for the work to make it easier to understand things related to the appearance and operation of the transformer. The main structure of this work are the parts of the transformer. The main part of the final work discusses the conditions that must necessarily be met, so that the transformers work in the parallel operation properly and under which conditions the transformers may not be located when their parallel operation is needed Measurements have been made in the laboratory and the procedure for their implementation is described. After each measurement, the results obtained were used for further computational analysis.