Resumen
Theoretical studies of electromagnetic processes in the active part of an electric machine's armature have been carried out in a dynamic short-circuit mode using a three-dimensional magnetic field model represented as a combination of electrical circuits of phase windings and a geometric 3D region. An approach was proposed to determine self- and mutual inductances between phases of the electric machine armature winding based on decomposition of electromagnetic processes by means of various combinations of powering the armature phase windings. Laws of electromagnetic processes resulting from self- and mutual effects of the armature phase currents causing appearance of effects of self- and mutual induction with and without taking into account magnetic properties of materials were established. The phenomena of self induction in phases of the armature winding, formation of components of induced currents in the phase as a result of action of currents in neighboring phases and their magnetizing and demagnetizing properties were considered. Influence of these processes leads to an asymmetry of the systems of mutual inductance between the winding phases. However, symmetry of total inductance of the armature phase windings is not violated. To determine with high accuracy inductive parameters of the electric machine armature winding according to the classical method, corresponding correction coefficients were proposed. This will minimize current errors and ensure adequacy of known widely used three- and two-phase models of electric machines based on systems of differential equations of the first order. Reliability and accuracy of the data obtained in 3D modeling of magnetic fields were confirmed by the results of physical tests. When taking into account magnetic properties of materials used in the active part of the electric machine armature, relative current errors did not exceed 2.68÷2.91 % and when magnetic properties were not taken in account, the errors measured 103.09÷106.32 %