THE POSSIBILITY OF IMPROVING THE DC ELECTRIC TRAIN POWER PERFORMANCE INDICATORS BY MODERNIZING THEIR POWER CIRCUITS

Abstract

The energy efficiency problem as applied to DC electric trains is considered. Constantly growing cost of electricity dictates the need to maximize the efficiency of its consumption. Most of the operating electric trains are equipped with a drive system having rather poor power performance characteristics, but with a certain margin for lifetime; therefore, their modernization is a topical issue. The article analyzes possible ways of modernization and their economic feasibility. Problem solution versions involving (i) replacement of existing traction machines by induction ones with a voltage inverter and (ii) modernization of DC motor control arrangements are described. The characteristic drive construction features are pointed out. It is shown that the induction traction drive is not only new electrical equipment, but a completely new philosophy of design solutions from the current collector to the underframe. A conclusion is drawn, according to which an AC drive is not a mandatory choice for medium-capacity and medium-speed traction applications and in often cases is even unprofitable. A comparison of drive reliabilities is carried out based on the operation statistics presented in the Accreditation Certificate of Hitachi Corp. In the considered case, the drive constructed using an induction motor and a voltage inverter would not have advantages in terms of reliability and cost. Therefore it is proposed to modernize the DC motor power control circuit by replacing the contactor equipment and use semiconductor switches. This alternative requires much smaller investment. At the same time, it becomes possible to fit electric trains with a rather intricate but efficient system of performance monitoring, diagnostics and protection of electric circuits, which will significantly improve the reliability and maintainability of the trains. An efficient traction electric drive suitable for these purposes has been developed and tested in operation. It can be installed on motor carriages without high cost and will result in significant improvement in all indicators of an electric train. Therefore it is expedient to use it in both operating electric trains in the course of modernizing them and in the newly produced ones.