A new, semi-analytic method of calculation of the electromagnetic field distribution in bars of convex cross-cross-section, with sinusoidal current flowing, has been presented. By omitting the Maxwell's displacement current the only problem to solve is the Helmholtz equations within the bar and Laplace ones beyond it. The solution is in the form of function series, with coefficients calculated based on boundary conditions. These functions are being solved at the edge into the Fourier series, and by comparing them we obtain the algebraic linear equation system (solved numerically). In the article the results and illustration of calculations for the bar of elliptical cross-cross-section have been presented.