Nauka ta progres transportu (Jun 2017)
CALCULATION OF MAGNETIC CHARACTERISTICS OF TRACTION ELECTRIC ENGINE WITH THE USE OF IMPROVED UNIVERSAL MAGNETIC CHARACTERISTICS
Abstract
Purpose. The article is aimed to develop a technique for calculating the magnetic characteristics of uncompensated traction electric motors (TEM) at any degree of attenuation of excitation based on the approximating expression for improved universal magnetic characteristics (UMC). It is also necessary to conduct an analysis of expressions for improved UMC with the aim of finding an expression that most fully satisfies the requirements for developing a technique for determining the inductive parameters of TEM. Methodology. It is necessary to determine the saturation coefficient for each degree of attenuation of the excitation for building the characteristics with the improved UMC. This can only be done analytically. To simplify the analytical finding of the saturation coefficient, the method based on solving a system of two equations is proposed, one of which is UMC itself, and the second one is a straight line whose angular coefficient is proportional to the saturation coefficient. Resulting values of the saturation coefficient for the excitation degrees β < 1 are essentially the coefficients of the shape of the magnetic characteristic. To get rid of the need to determine the coefficients of approximation each time in the calculation of characteristics a form of improved UMC is proposed, in which the magnetomotive force (MMF) of the excitation winding serves as the argument's role. Findings. Using the improved UMC it is possible to calculate the characteristics of uncompensated TEMs for any degree of attenuation of excitation. The accuracy of the calculation at β = 1 does not differ from that in the calculation for UMC, proposed by Prof. M. D. Nakhodkin. The same accuracy is preserved at excitation degrees that are different from unity. Originality. An analytical technique for calculating the magnetic (speed) characteristics of uncompensated TEM for any degree of attenuation with the help of an improved UMC is proposed. The analytical technique for determining the saturation coefficient for an improved UMC at any degree of attenuation of excitation is also proposed. Due to the introduction of an excitation winding as an argument, there is no need to determine the approximation coefficients for each specific TEM. Practical value. The developed methodology let calculate magnetic characteristics of uncompensated REMs for any degree of attenuation of excitation. On the basis of this technique, it is possible to develop a technique for determining the inductive parameters of the TEM, using the saturation coefficient of the machine as initial data.
Keywords
