AN EFFICIENT WAY OF SHUNTING THE MAGNETIZING COILS OF TRACTION MACHINES

Abstract

Continuous and significant increase in the cost of energy resources dictates the need of consuming them with the maximum possible efficiency. The suburban railway communication, which is realized by means of electric trains, is of key importance in transport connection of large cities in Russia with regional populated localities. It is exactly suburban railway transport for which the availability of regenerative braking and improvement of its efficiency is the most topical issue, because unlike electric locomotives, electric trains , have a large number of stops at stations; therefore, they have to operate in acceleration and braking modes quite frequently and in a wide range of speeds. The railroads of the largest megalopolises of the Russian Federation, first of all, Moscow and St. Petersburg, have DC power supply and consume the largest amount of electricity; therefore, the power performance indicators of electric trains should be improved. In designing the modern domestically produced trains it was supposed that with increasing the technical speed of trains up to 72 km/h, their traction and power performance indicators will be better than those of electric trains of the previous series. But in reality, the expected increase in technical traveling speed did not occur: it remained at the level up to 55 km/h. As a result, the effect from using regenerative braking decreased from 20 to 10%, and shortcomings of the previous series, on the contrary, revealed themselves especially strongly; in particular, rheostatic losses increased from 10 to 20%. This circumstance served as the basis for development of an energy saving system of the traction electric drive (ES TED), which was elaborated executed by MPEI specialists with participation of the Riga Electro-Machinery Construction Works and the Moscow Railroad. The regrouping of traction machines (TM) and an energy saving algorithm of start-up are implemented in the ES TED system by joining two motor cars the design of which did not foresee regrouping of the traction cars.. As a result, the energy consumption from the external power supply system was reduced to 30% while preserving of the already available advantages. As regards the expenses required for modernizing the serially produced trains by fitting them with the ES TED system, they are quite low. A modernization version of the ES TED system is proposed that involves the use of electronic shunting devices on the basis of IGBT transistors instead of the inductive shunts (IS). The electronic shunts (ES) can operate continuously without being overheated; they provide the best conditions for the course of transients and possess a number of advantages over IS. By applying ES in electric trains equipped with the ES TED system it will be possible not only to solve the problem of IS overheating, but also to improve the conditions for transients in the TM. In addition, a higher response speed and better reliability of system operation will be achieved, and it will become possible to control the traction machine's magnetizing coil shunting in a wide range.