Abstract: The article presents selected voltage waveforms in a railway traction network with a nominal voltage of 3kV. The waveforms were recorded during the operation of an EN-57 train with a chopper drive system and while the vehicle was stationary. The influence of the current drawn by the rail vehicle on the instantaneous voltage values in the railway power supply network is presented. Particular attention is paid to the current and supply voltage waveforms of the vehicle while passing under an insulator separating power supply sections. This is a very dangerous moment during train operation, as the resulting overvoltages and current surges negatively affect the network and the vehicle’s converter.1. INTRODUCTION
Manufacturers of electric traction vehicles are increasingly equipping their vehicles with power electronic drive systems. These allow for the smooth delivery of energy to the vehicle’s motors, which is characterized by greater ride comfort as well as lower energy consumption, especially in cases where the vehicle must cover a given section at a reduced speed (e.g., in mountainous areas). In order to reduce the vehicle’s speed in a classic solution, a resistor is switched into the motor’s current circuit. The thermal energy generated in the resistor as a result of the traction current flow is wasted energy.
The most common power electronic (converter) drive systems are solutions enabling the powering of a DC motor (so-called chopper drive) and a three-phase induction motor (so-called inverter drive) [1, 2].
Drive systems controlling permanent magnet motors are also encountered.
The use of a power electronic drive system imposes many requirements that the traction vehicle converter must meet. Due to the large number of switching operations of semiconductor power transistors used in the construction of the converter and the large commutated currents, the phenomenon of electromagnetic interference generated by the vehicle occurs.
Therefore, before being approved for use, the converter must meet electromagnetic compatibility requirements.
The power electronic converter is a pulse system, therefore the current drawn for power supply also has a pulse character. To mitigate this phenomenon, a capacitor with low inductance and high capacitance, as well as a choke to smooth the waveform of the drawn current, are used directly at the terminals of the power transistors. (…)
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Source: Logistyka Magazine