Andreas Nagel

A new family of modular IGBT converters for traction applications

Electrical locomotives and trains are nowadays driven by asynchronous motors, which are fed by voltage source inverters. The IGBT two level inverter allows a standardization of the topology and the control strategy over the whole power and voltage range. However, different application conditions (cooling, dc-link voltage, power range) lead to different converters. To allow a flexible converter design with proven components, a family of power electronic building blocks was developed, which uses 3.3 kV and 6.5 kV IGBT and achieves an output power of up to 3 MW

Challenges in using the latest generation of IGBTs in traction converters

Summary The voltage class 6.5kV was the last step to now cover completely the whole range of voltages for traction starting with 1.7kV and 3.3kV. This lead to the general introduction of the IGBT across the whole power range of traction. In first IGBT generations the Non Punch Through design dominated here. The latest generation of IGBTs feature characteristics like field-stop design or trench design. Thus high cosmic ray withstand capability can be combined with low VCesat. For the high-power high-voltage application as used in traction, the introduction of the field stop leads to a significant change in the switching behavior compared to the conventional NPT-design. It will be shown how the IGBT and diode turn-off characteristics change and how sensitive it is to parasitic circuit characteristics. Especially in high-power circuits with relatively large stray inductances, this is a device and application challenge. Further more it will be shown that the IGBT overvoltage during turn-off transients can be controlled only by using a highly dynamic gate driver. Since no active control ofthe diode turn-offis possible, the peak-voltage must be limited by appropriate circuit and device design. For new generations of IGBT and diode, this behavior should be considered carefully by the semiconductor development.

Next generation of IGBT-modules applied to high power traction

Modern high power traction converters are equipped with IGBT-modules. For a reliable operation the modules have to fulfil the following requirements: High junction temperature limit, large safe operating area, high surge current capability and sufficient thermal cycling capability. In this paper current and next generation of IGBT modules will be characterised regarding the first three aspects.

Multicommutation of IGBTs in large inverters

Large inverter-systems are characterized by a significant number of parallel IGBTs operating on the same dc-link. The IGBT-phases are cross coupled by their mutual stray inductance. This paper investigates the special effects occurring due to nearly simultaneous switching of multiple IGBTs. This operation can cause a significant increase in stress on the IGBT and on the free wheel diode. Countermeasures to cope with these problems are discussed

Latest developments in increasing the power density of traction drives

Volume and weight of the propulsion equipment of a traction drive are most important features to provide more efficient transportation in the future. It will be shown how the converter technology for traction drives has improved its performance in the past decades and new developments are presented promising a further increase in power density. The machine and corresponding gear and suspension system is even more weight sensitive, and latest measures to increase the performance will be presented.

A new standard IGBT housing for high-power converters

In the field of high-power converters, the standard IGBT module housing is the Ihm / Ihv established by Eupec during the 1990s. This paper explains the limitations of this housing and presents approaches for a new, next-generation housing. This new housing design targets a reduction of the leakage inductance and a significant power density improvement. With regard to the highest power densities for high-power traction converters, initial results are shown for converters using a reverse conducting diode controlled (RCDC) IGBT.

Robustness requirements on semiconductors for high power applications

Robustness of power semiconductors is a key parameter for reliable converter operation. This paper discusses the main robustness characteristics limiting the performance in high power converters. It shows necessary design precautions for the circuit design and also explains where the semiconductor manufacturer has to improve the devices with the aim of maximum electrical exploitation of the semiconductor.