Modern train traction systems use high-speed
switching IGBTs in main circuits. High-speed switching reduces electromagnetic
noise generated by the main motor and improves the efficiency of energy
conversion. For the inverter control system, vector control is employed to
control the torque current component and the exciting current component
separately, which are output to the induction motor. Since vector control
ensures high-speed torque control, it is also applied to slip-slide control to
improve adhesion force. The maintenance work for contacts and pneumatic parts
can be eliminated by replacing mechanical contacts in each unit with electronic
contacts and by changing the pneumatic operation system to an electromagnetic
one. The numerous advantages of insulated gate bipolar transistor (IGBT) power
modules and their ongoing development for higher voltage and current ratings
make them interesting for traction applications. These applications imply high
reliability requirements. One important requirement is the ability to withstand
power cycles. Power cycles cause temperature changes which lead to a mechanical
stress that can result in a failure. Lifting of bond wires is thereby the
predominant failure mechanism. A fast power cycling test method activating the
main failure mechanism has been developed which allows reproduction of millions
of temperature changes in a short time. The applicability of fast testing is
supported by a mechanical analysis.
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