Papers by Keyword: Robustness

Abstract: A comparative study of state-of-the-art commercial 1200V trench-gate, planar-gate, and trench-assisted planar Silicon Carbide (SiC) MOSFETs is presented. The experimental study mainly focuses on disclosing the static and robustness characteristics of distinct SiC technologies targeting automotive applications under room and high temperatures. The benchmark study of static characteristics covers specific on-resistance (R_ON,SP), gate leakage (I_GSS​), drain leakage (I_DSS​), breakdown voltage (BV_DSS​), and drain-induced barrier lowering (DIBL) effects. The avalanche robustness is investigated by the unclamping inductive switching (UIS) setup under 25 °C and 175 °C while the single-pulse and repetitive short-circuit capability is evaluated under hard switching fault (HSF) under 25 °C.

Abstract: This work deals with Robust design optimization (RDO) under interval uncertainty and the resolution of such problems using a Bayesian optimization algorithm. In metal forming, process parameters such as tool radius, step size, or forming toolpath introduce variability that directly affects the final geometry and quality ofthe formed parts. In this context we aim at finding a design minimizing the amplitude of the performance interval but such a formulation does not account for the nominal performance. In this work, we introduce a scalarized objective adapted to the proposed algorithm allowing it to identify a Pareto optimum of both stability and nominal behavior. We propose an efficient expected improvement (EI) estimator for this objective based on an extreme-value approximation of surrogate extrema. The approach is illustrated on an analytical test problem and on a forming simulation with spring-back, where the new objective yields more practically relevant solutions than a variation-only robustness criterion.

Abstract: This research addresses key challenges in progressive collapse prevention by introducing an advanced method to enhance the complex structural systems monitoring. The study focuses on variation of deformation work patterns with the aim to identify the most critical load paths while a random element within the structure undergoes damage. A comprehensive mathematical model has been developed to analyze changes in load paths due to damage in structural elements. The method utilizes an energy-based metric introduced by De Biagi and Chiaia, allowing for a detailed assessment of damage progression. The damage is simulated through the alteration of the stiffness of structural elements by applying progressive cross section reduction. The predictions of the model were validated through its application to simple systems composed of rods, where changes in load paths were observed as damage advanced in random elements. For more complex structural systems, the method was applied using numerical simulations, providing a detailed evaluation of its performance in more load cases scenarios. The proposed metric effectively captures the effects of localized damage and its propagation through the system, offering valuable insights for the monitoring and prevention of progressive collapse. The method yields two significant outcomes: first, mapping the variation of deformation work with respect to the damage allows for the visualization of the variation in the load path during the damage of a random element within the structure, thus, identifying which elements are loaded and which are unloaded; second, the study of evolution of the variation of deformation work with respect to the damage for different stiffnesses allows identifying the value of critical stiffnesses that determine whether the element remains part of the main load-bearing path. In this work, the method is applied to 2D and 3D truss systems, which are representative of critical infrastructure like bridges and towers, as well as to ad hoc designed structural schemes created to highlight specific aspects and demonstrate the effectiveness of the method. The aim of the method is not only to ensure the safety of vital infrastructure by improving resilience against catastrophic events, but also to offer practical insights by identifying the most critical areas for sensor placement, enabling optimal monitoring and early detection of failure points.

Abstract: The aim of this study is to investigate the overcurrent turn-off robustness limit of SiC MOSFETs from three different manufacturers with three different cell technologies up to very high turn-off currents to determine a possible destruction limit and failure type. The influence of the negative gate-source voltage (V_GS,off) was studied because of the high drain-source overvoltage in connection with the decreased V_GS,off, which is the most critical point for the gate oxide field stress for the different cell technologies. All measurements were performed at a positive gate-source voltage (V_GS,on) above the specified datasheet values to reach high currents without channel pinch-off. In addition, the influence of temperature on the overcurrent robustness was studied. Finally, TCAD simulations were performed to determine the reason for the failure mechanism under the overcurrent turn-off conditions. All the manufacturer devices can withstand several times higher gate-source voltages under overcurrent conditions than the values recommended in the datasheet.

Abstract: Silicon carbide (SiC) MOSFETs are gaining more and more market share in typical silicon (Si) IGBT applications such as traction or renewable energies. Especially in reliability sensitive traction applications, medium voltage IGBT-modules (3.3 kV-6.5 kV) are widely used and introducing SiC-MOSFETs to such industries is the next self-evident step already on the way. While their superior electrical performance has been generally accepted already (e.g. [1]), SiC-modules have not yet established a track record of high reliability in this voltage class. For this study, 3.3kV SiC-MOSFET-switches were compared to standard Si-IGBTs regarding their humidity robustness under high voltage bias. Both chip types had been assembled in the same traction rated packages to exclude this influence. The Si-IGBTs resembled the well-known industry standard performance, while the SiC-MOSFETs show no degradation within the reported test time of 2000 h. Given the fact [2], that the latest Si-IGBT generation offers a much better humidity performance as well, the standardised HV-H³TRB is no longer sufficient to provoke failures within a reasonable testing time. On the one hand, this suggests that humidity driven failures will not be an issue under field conditions anymore. On the other hand, even harsher tests are required to investigate differences in humidity performance.

Abstract: This work addresses the electrical behaviour of high-voltage (HV) SiC MOSFETs, being the main motivation to check their robustness. Large area (25 mm²) devices rated for 3.3 kV applications were fabricated with a special process for the gate oxide formation. The unit cell was designed to achieve good short-circuit performance. Static and dynamic characterization is presented at room and high temperature. Output curves and 3^rd quadrant behaviour were analysed. Dynamic tests were performed at high bus voltages and high current. To check device robustness, short-circuit and power cycling’s were considered. Robustness test results put in evidence the achievement of reasonable good results obtained due to a suitable cell design.

Abstract: Accordance with a new EN 1992 the robustness of the structural systems must be analyzed. When applying proposed new strategy, it has been verified that the structure has sufficient redundancy and possibility to mobilize so-called alternate load path (AP-method). Paper presents a modified complex method for robustness estimation in case of the RC-structural systems. Proposed pseudo-static method based on the energy-saving approach. Paper also presents a full probabilistic pseudo-static nonlinear method which was developed for structural robustness assessment, taking into account the statistical variability of the materials properties and, as a consequence, parameters of the plastic hinges and possible failure modes.

Abstract: This paper presents a preliminary study of the impact of device electro-thermal parameter spread and temperature variation on the robustness of SiC MOSFET parallel multi-chip power switch architectures. Reference is made to 1200 V – 80 mΩ rated commercial devices. Some major parameters are identified and selected, presenting experimental evidence of their impact during transient overload events. An advanced physics-based simulation model is then employed to extend the analysis to a more comprehensive set of parameters and operational conditions.

Abstract: Nowadays, the interest on structural robustness is increasing because of the recent terroristic attacks. Although a large number of research projects have been carried out in this field, limited design guidelines as well as code recommendations are nowadays available. Leading to the fact that the design for robustness is far from being current practice. Conversely, the design for natural hazards as the earthquake is a well-consolidated practice and modern codes implement effective and well-recognized design rules. Even though seismic design philosophy based on the concept of hierarchy of resistance enables structural robustness for conventional structural systems, this is not demonstrated for structures equipped with anti-seismic devices as well as innovative dissipative systems. Recently, the use of friction based dissipative joints has been proved to be a promising solution for seismically design steel moment resisting frames. However, the robustness and the resistance against impact loading of this type of joints is not yet investigated. With the aim to develop an experimental campaign based on impact tests, preliminary finite element analyses have been carried out to identify the main criticisms and to drive the rational design of the joint specimens. With this regard, in the present paper, the results of a numerical parametric study on the preliminary push-down test are presented and discussed.

Abstract: In this paper, a design procedure that combines both progressive collapse design under column removal scenario and capacity design to produce a hierarchy of design strengths is presented. The procedure develops in the context of the European Standards, using the classification of European steel sections and considering the seismic design features. Three-dimensional models of typical multi-storey steel frame buildings are employed in numerical analysis. The design for progressive collapse is carried out with three types of analysis, namely linear static, nonlinear static and nonlinear dynamic. Since the behaviour following sudden column loss is likely to be inelastic and possibly implicate catenary effects, both geometric and material nonlinearities are considered. The influence of the fundamental parameters involved in seismic and robustness design is finally investigated.