There is the design features and the main methods of decrease the general and local losses in power transformers tanks from the concentrated magnetic fields of the powerful current leads is submitted. Mathematical statement of tasks electromagnetic and thermal processes calculation of is given. The main approaches to numerical modeling of losses in constructional not magnetic and ferromagnetic still are presented by methods of superficial and volume losses. Numerical and analytical solutions of a number of regional tasks for systems of the not magnetic and ferromagnetic plates, which are elements of a design of covers of tanks are provided. Known empiric-analytical estimates of coefficients of a thermolysis, and also experience of application of the CFD method of modeling of problems of a heat mass transfer for calculation of heating of elements of a design of a tank are presented. The main approaches to development are described by means of ANSYS of settlement models of the transformer equipment. Results of numerical researches and their comparison to measurements on natural samples of powerful power transformers are presented.