Surface magnetic charge method combined with spatial harmonic expansion for magnetic field analysis of deflection yokes

The surface magnetic charge method and the Fourier spatial harmonic expansion technique for three-dimensional magnetic field calculations are studied. Spatial harmonic components of the magnetic fields generated by the magnetized ferromagnetic core of deflection yokes were derived by the surface magnetic charge method. Because of the orthogonality of harmonics, a concise and straightforward relation between each harmonic of the fields and that of the surface magnetic charges was obtained. By this method, the two-dimensional integral equations for magnetic charges are reduced to one-dimensional equations, one for each order of charge harmonics. A program was written for the calculation of magnetic fields of the deflection yoke. An example was calculated, and some useful conclusions were obtained from the results