Method for representing the electromechanical characteristics of an electric traction drive with sequentially excited DC motors

Abstract: The shortcomings that occur during the construction of the electromechanical characteristics of a traction electric drive with DC motors of series excitation are presented. An analysis of known methods of constructing the specified electromechanical characteristics is carried out, such as by universal characteristic, by known catalog data of the engine. Based on the analysis, a number of shortcomings of known methods of constructing the electromechanical characteristics of a traction electric drive with DC motors of series excitation and their inconsistency with existing requirements are revealed. The dependence of the magnetic flux of DC motors with series excitation on the load on the shaft is the cause of the nonlinearity of their electromechanical characteristics. Factories - manufacturers of such engines provide experimentally obtained universal characteristics (expressed in relative units). Using them, it is possible to construct a universal mechanical characteristic, from which it is possible to proceed to the characteristics of the selected engine. To do this, it is necessary to multiply the values I, M and ω laid out along the axes by their nominal values. In this case, it is usually necessary to change the scale grid of the graph, since the previous one will correspond to the fractional value of the quantities plotted on the axes. The presented method of constructing electromechanical characteristics according to the universal characteristic has an error of up to 30%, which is associated both with the nonlinearity of the electromechanical characteristics of DC motors with series excitation, and with the need for a graphic transition from the universal characteristic to the characteristic of a specific traction motor. The method of constructing electromechanical characteristics according to catalog data has similar disadvantages. A method of constructing electromechanical characteristics analytically is proposed, which allows avoiding the disadvantages.