The core is an essential part of transformers, generators, motors and other electrical equipment. Magnetic flux core and voltage are used to start the engine, the production of electricity and turns into a transformer. Magnetic materials are used as components of electrical products, which have the primary task of directed conduct magnetic flux and thereby enable electromagnetic conversion underlying the function of these products. Grain oriented electrical steel is mainly used as the active material in the magnetic cores of electric transformers, due to the high magnetic permeability and the low "core loss" (loss of power in the form of heat that occurs due to scattering phenomena acting on the material during the process of magnetization). Currently, the most attractive and affordable technologies for the production of Grain oriented electrical steel are based on "acquired inhibition" strategy. The potential to reduce losses associated with all three losses (anomalous losses, eddy current losses and hysteresis losses) and following are: thin magnetic sheet (without destabilizing secondary recrystallization), a smooth surface sheet (adaptation between the steel and the insulation layer), sharper textures with improved grain structure (generating micro grains, control of particle shape), improving coating with increased stress and optimization of laser treatment of sheet surface. One of the instruments of control and quality assurance of the Grain oriented electrical steel from the manufacturer of transformers, which comes from the outside and enters the production process are "the Technical Co-supply conditions. The technical delivery conditions defined magnetic properties, geometric characteristics, technological characteristics, tolerances, test procedures, conditions of delivery and packaging method of the magnetic sheet in the final annealed condition. Typically for three-leg "Step-lap" cores, Building factor of distribution transformers is around 20%, and for the core of power transformers around 10%. In order to reduce losses and noise, the number of sheets in the layer should be as small as possible, a number of steps as much as possible. Because productivity is the number of sheets in the layer usually 2-3, and the number of layers in a cycle 3 - 7th.