MECHANICAL POWER OF TRACTION ELECTRIC DRIVES OF MAINLINE ELECTRIC LOCOMOTIVES

Abstract. The mechanical power of traction electric motors of mainline electric locomotives with a supply voltage of 25 kV is determined by the efficiency when powered from a multi-arm single-phase semi-controlled thyristor rectifier, the arms of which are connected to separate sections of a traction single-phase transformer. Purpose: to obtain an analytical expression for calculating the coefficient of reduction of mechanical power of traction electric motors under the condition of maintaining the nominal thermal regime of the motors. The task is to determine the quantitative influence of armature current harmonics on the mechanical power of traction motors. Methodology. The determination methodology is based on the law of conservation of energy, the method of harmonic analysis of the pulsating current of the armature winding, methods from the theory of electric machines and the method of computer modeling to obtain experimental dependences of the pulsation coefficient of the armature current on the control angle of thyristors, the inductance of the armature circuit and the load current. Results and their scientific novelty. A computer model of a thyristor electric drive has been developed, on the basis of which experimental graphical dependences of the armature current ripple coefficient on the thyristor control angle, armature circuit inductance and load current have been obtained. For the first time, an analytical expression for the coefficient of reduction of the mechanical power of a DC traction motor when powered by single-phase semi-controlled thyristor rectifiers has been obtained, taking into account the current ripple coefficient, based on the calculation of relative electrical losses from the harmonic components of the current, which are equal to the square of the current ripple coefficient. An analytical expression for calculating the armature current ripple coefficient, taking into account the thyristor control angle, armature winding inductance and load current, has been further developed. Practical significance. The analytical expression for determining the coefficient of reduction of the mechanical power of a DC motor when powered by a single-phase half-controlled thyristor rectifier allows: 1) to calculate the load capacity of the traction motor by mechanical power on the shaft, taking into account the permissible heating by the effective value of the current with harmonic components; 2) to calculate the inductance of the smoothing reactor to increase the mechanical power of the motor by reducing the current ripple coefficient.