How to supply power for traction transformer

Traction transformer is one of the core equipments in railway electric traction system, which is widely used in electrified railways. Its main function is to convert the voltage in high-voltage transmission system into a voltage level suitable for electric locomotives, so as to realize stable and efficient power supply to the traction system. In this paper, the basic structure, working principle of traction transformer and its role in railway power supply system will be expounded.

First of all, traction transformer is usually installed in traction substation, and its input end is connected to the national grid or regional high-voltage transmission lines. The common input voltage level is 110kV or 220kV. The output end is connected to the catenary system through the feeder, which provides single-phase alternating current to the electric locomotive. The common output voltage is 27.5kV or 55kV (when the double-track power supply is provided). Because the traction load has the characteristics of large fluctuation and obvious single-phase load, the design and operation of traction transformer should consider its particularity.
　　he working principle of traction transformer is similar to that of ordinary power transformer, and voltage conversion is based on electromagnetic induction principle. When high-voltage alternating current passes through the primary winding, an alternating magnetic field is generated in the iron core, so that a corresponding proportion of low-voltage alternating current is induced in the secondary winding. The difference is that traction transformers usually use three-phase single-phase or single-phase single-phase wiring to balance the power grid load, such as V/v wiring, Scott wiring and other structures, in order to reduce the asymmetric impact on the three-phase power system.
　　n the process of power supply, after the traction substation receives the electric energy from the state grid, the traction transformer first steps down the high-voltage current, and then directly transmits the electric energy to the catenary through the rectifier (in the DC traction system) to provide power for the electric locomotive. In the AC traction system, there is usually a main transformer inside the electric locomotive to further reduce the voltage for the traction motor.
　　In addition, the traction transformer also has good overload capacity and high reliability to adapt to the current impact caused by frequent starting and braking in railway transportation. At the same time, in order to ensure the safety of power supply system, traction transformers are usually equipped with perfect protection devices, such as over-current protection and differential protection, to prevent equipment from being damaged by short circuit or abnormal operation.

To sum up, traction transformer plays a vital role in the power supply system of electrified railway. It not only realizes the voltage level conversion, but also effectively ensures the safety and stability of train operation, and is an indispensable and important equipment in modern rail transit system. With the development of railway technology, the design and manufacture of traction transformer are constantly optimized, moving towards a more efficient, environmentally friendly and intelligent direction.