Comparison of three-phase transformers with rectangular and circular conversion of laminated magnetic cores (active power losses)

Abstract

Purpose. In the mass production of low-power transformers, magnetic cores and windings are used with rectangular sections of rods and forming the contours of the coils turns. The contours of medium and high power transformers active elements are circles. The cross sections of the magnetic cores form rectangular steel packages of various widths with filling coefficients of circular circuits 0,786–0,925 at a power of 16–10000 kV·А. In recent decades, rectangular contour generators of planar electromagnetic systems have also been used in the transformers manufacture with a more than 250 kV·A capacity. The use of rectangular sections instead of rods circular cores changes the consumption of materials and active power losses. Therefore, it is of theoretical and practical interest an analytical substantiation of the expediency of such a replacement. Methodology. A comparative analysis of hree-phase transformer variants is performed by the method of generalized invariant structural-parametric synthesis. Target functions are used with a component of the source data and electromagnetic loads and dimensionless components. The dimensionless optimization components of mass and cost are functions of relative geometric controlled variables. The loss component additionally depends on the relative electromagnetic controlled variable. The values of optimization components are indicators of the objective function, and their minima represent the technical level indicators of transformer. Results. The indicators are determined with same source data and loads, which corresponds to electromagnetic power of the compared options identity. Calculations are performed in real range of electromagnetic controlled variable variation of dry and oil transformers. This eliminates the dependence of loss indicators on power, method of heat removal and other factors. Originality. It has been established that, in addition to improving the mass-carrying indices, a reduction in losses of three-phase transformers is achieved when replacing circular forming circuits to rectangular circuits. Practical value. The reduction of loss of transformers of voltage range 1–110 kV with rod laminated magnetic cores, copper and aluminum windings with rectangular generating circuits relative to analogs with circular circuits is 6,3–8,9 % and 2,64–3 % with the rods filling factor 0,786 and 0,925.