Determining the Switching Frequency of a Transistor Converter for a Traction Collector Motor
Abstract
The purpose of this work is to determine the switching frequency of a transistor converter for a traction collector motor of a locomotive based on the criterion of permissible current ripple. The stated goal is achieved by solving the following problem: a methodology for determining the consideration of changes in motor parameters when calculating the switching frequency of the transistor converter is proposed. The peculiarity of the proposed approach is that it takes into account the degree of saturation of individual parts of the magnetic system of the electric motor. The most significant result is an increase in the accuracy of calculating the switching frequency by taking into account the change in the inductance of the commutator motor windings when the degree of saturation of the magnetic system changes. The switching frequency for a DC traction motor with a pulse converter is calculated. Two main operating modes of the electric motor are considered: with full magnetic flux and with weakened magnetic flux. As a result of calculations, it was established that the dependence of switching frequency on currents is nonlinear. For the operating mode of the electric motor with full magnetic flux, the switching frequency is determined taking into account the processes in the field winding circuits and in the armature circuit windings. The most important results are the determination of the switching frequency of the pulse converter for powering and regulating the traction motor in all operating modes. The proposed methodology allows the selection of transistor devices for the converter according to the switching frequency.
