Propulsion Systems for modern high-speed trains and urban transport networks rely on energy efficient traction motors driven by electronic inverters for smooth torque control.
The control electronics consists of three basic sub-systems:
- a rectifier for the supply voltage
- a DC Link with a capacitor bank and inductors for energy storage and filtering
- the converter based on a variable frequency drive
A DC-Link capacitor has to store enough energy to ensure that a stable voltage is supplied to the converter in all conditions and possible load currents. Film capacitors are the first choice for this task due to their intrinsic low ESR, high RMS current capabilities, overvoltage withstanding and high reliability.
Moreover the rapid development of fast switching semiconductors generates ripple currents with high energies and frequencies. Resonant filters using low inductive film capacitors keep this harmful noise away from motor coils and supply networks.
Film capacitors are the first choice for every power supply which requires a set of capacitors dedicated to power conversion, filtering EMI clearing and feedback loops.