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**"Modelling and simulation of a DC electric traction system"**

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**Author:**

**A.Szeląg, Institute of Electrical Machines, Technical University of Warsawa, Poland**

A simulation computer model of a DC electric traction system is presented. Because of the complexity of the system and a great number of variables, the program (written in Fortran) is designed to calculate instantaneous, average and RMS values of voltages in the contact line, line drops, currents of vehicles and substations, traction energy consumtion, the loss of energy in line, speeds and positions of vehicles.

The progam algorithm is based on the instantaneous schemes method. This method divides the continuous process: flow of current in the contact line and running of traction vehicles into a series of time intervals and corresponding values of current, acceleration, vehicle speed, etc. (time-independet variables).

In calculations of the DC traction feed system the voltage at the vehicles’ pantograph has usually been assumed as average. This causes mistakes because of neglect of the influence of voltage on the current and time of vehicles’ running. Also, in many cases for electric railway traffic the real instantaneous power of a locomotive, which depends on the voltage at the pantograph, is important. The problem has been dealt with in the simulation program presented. Some simulation experiments making use of the program are included.