Michel Mermet-Guyennet

Temperature measurement on series resistance and devices in power packs based on on-state voltage drop monitoring at high current

Based on the on-state voltage drop monitoring at high current, an alternative method for thermo-sensitive parameters calibration is reported. The main goal is that it allows the simultaneous calibration of the series resistance and power devices voltage drop on temperature. Thereby, the average temperature over all power devices and the temperature difference in average inside the pack can be measured in real applications.

New Technique for the Measurement of the Static and of the Transient Junction Temperature in IGBT Devices under Operating Conditions

A novel technique is presented, which uses dIce/dt and the transconductance as a thermo-sensitive parameter for the measurement of the static and of the transient average junction temperature in IGBT devices. The paper describes the physics of the signal generation, provides the experimental setup, and discusses the accuracy and the suitability of the technique under operating conditions of the devices.

Measurement of the transient junction temperature in MOSFET devices under operating conditions.

Abstract The capabilities of three techniques to measure the transient average junction temperature in power MOS devices based on the electrical thermo-sensitive parameters are assessed experimentally and by compact device simulation. The first two methods make use of the dependency of d I d s /d t on the temperature, while the third one exploits the temperature dependency of the turn ON delay of the device.

Analysis of Clamped Inductive Turnoff Failure in Railway Traction IGBT Power Modules Under Overload Conditions

This paper studies the overload turnoff failure in the insulated-gate bipolar transistor (IGBT) devices of power multichip modules for railway traction. After a detailed experimental analysis carried out through a dedicated test circuit, electrothermal simulations at device level are also presented. The simulation strategy has consisted in inducing a current and temperature mismatch in two IGBT cells. Results show that mismatches in the electrothermal properties of the IGBT device during transient operation can lead to uneven power dissipation, significantly enhancing the risk of failure and reducing the lifetime of the power module. Concretely, simulations qualitatively demonstrate that localized hot-spot formation due to a dynamic breakdown could lead to a second breakdown mechanism.

Long-Term Reliability of Railway Power Inverters Cooled by Heat-Pipe-Based Systems

This paper analyzes the impact of a nonuniform temperature distribution inside insulated-gate bipolar transistor (IGBT) power modules on the reliability of railway power inverters. The interaction between the chosen cooling system (a heat-pipe-based one) and the power module is considered in detail. After showing the experimental setup and thermal conditions, thermal mapping inside the power module is carried out. Then, the effects of the thermal cycles on the constitutive elements of the IGBT module are pointed out when considering a real mission profile. Finally, the experimental results from the thermal cycles are linked to problems on the power-inverter reliability. Concretely, the thermal-grease distribution is analyzed on failed IGBT modules coming from the field, and the solder-delamination pattern observed in IGBT modules after endurance cycling tests is also reported.

Compact modelling and analysis of power-sharing unbalances in IGBT-modules used in traction applications

IGBT modules are critical components for the reliability of power converters used in traction applications. A thorough analysis of all stressful operating conditions is a complex task, which requires versatile simulation capability. In this paper a comprehensive electro-thermal model of an IGBT-module is developed. Then, circuit simulation is used to investigate the power sharing between parallel chips during transient operation. Unbalances are observed, their causes identified and their influence on device degradation pointed out and discussed.

New power technologies for traction drives

This paper discusses the needs of power technologies for traction drives with the view of the rail market requirements. A particular case is discussed in detail : the very high speed train concept developed by Alstom and called AGV. Some potential developments with new technologies are described to improve the performance of high speed traction drives.

Failure-relevant abnormal events in power inverters considering measured IGBT module temperature inhomogeneities

In this work, temperature inhomogeneities inside IGBT modules are measured to assess their relevance for the component reliability. Such issue has not been considered in many previous studies, since it is often assumed that the electro-thermal characteristics of IGBTs compensate for such temperature differences. Starting from real temperature measurements, this work discusses such aspect aided by electro-thermal simulations. This method provides useful information for the reliable thermal design of power modules, also considering the actual cooling system.

IGBT module failure analysis in railway applications

This work reports two different characteristic patterns detected in IGBT chips failed in real operation (railway application) by failure analysis procedures. The analysed chips have been recovered from the rheostatic chopper leg and from the three legs which supplies the traction motor. It is observed that depending on the location and characteristics of the detected default (burn-out spot), this failure can be attributed to a latch-up process or a secondary breakdown mechanism. These results are corroborated with tests at limit, obtaining the same result. Consequently, each failure can be linked to overcurrent (latch-up) or overtemperature (secondary breakdown) events, which makes possible to distinguish between problems coming from driving strategies or thermal issues (uneven temperature distribution inside the module or packaging wear-out).

Revisiting power cycling test for better life-time prediction in traction

This paper discusses the commonly accepted method for life-time prediction for power converters in traction. The method is based on junction temperature estimation and thermal cycles on a given duty cycle. The predicted numbers of thermal cycles are compared to the curves giving the number of cycles to failure versus temperature cycles. These curves are extrapolated from power cycling tests. Power cycling tests and extrapolation method will be discussed, particularly under the aspect of failure mechanisms that are induced. In order to generate the same failure mechanisms in power cycling than in the real applications, a new power cycling approach is presented.