Single pulse avalanche robustness and repetitive stress ageing of SiC power MOSFETs

This paper presents an extensive electro-thermal characterisation of latest generation silicon carbide (SiC) Power MOSFETs under unclamped inductive switching (UIS) conditions. Tests are carried out to thoroughly understand the single pulse avalanche ruggedness limits of commercial SiC MOSFETs and assess their aging under repetitive stress conditions. Both a functional and a structural characterisation of the transistors is presented, with the aim of informing future device technology development for robust and reliable power system development

Individual device active cooling for enhanced system-level power density and more uniform temperature distribution

This paper provides a method of individual device active cooling system to balance the temperature distribution of system-level power density. 3L-ANPC GaN inverter was used to test and prove the feasibility of it in using multi-level systems

GaN HEMT gate-driver for achieving high power converter integration levels

This work proposes a solution for implementing an isolated gate driver for GaN HEMTs based on the previous topology for SiC power MOSFETs. The isolation of the gate driver is realised by the single transformer topology with double winding in the secondary side. The Bi-level HF Amplitude Modulation scheme is retained to avoid the core saturation as well as providing simultaneously both the switching signal and the required gate power in the secondary side which ensures the full range duty ratio. The reconstruction of the original PWM signal is optimised using a simple hysteresis comparing scheme, which is the Schmitt Trigger circuit, to avoid sudden turn-on or turn-off. The experiment result shows that the Schmitt Trigger circuit could effectively avoid the sudden turn-on or turn-off but it might have some negative effect on the accuracy of duty circle. Finally, the feasibility of the gate driver is demonstrated with the PGA26E19BA GaN device with optimised final power stage

Avalanche ruggedness of parallel SiC power MOSFETs

© 2018 Elsevier Ltd The aim of this paper is to investigate the impact of electro-thermal device parameter spread on the avalanche ruggedness of parallel silicon carbide (SiC) power MOSFETs representative of multi-chip layout within an integrated power module. The tests were conducted on second generation 1200 V, 36 A–80 mΩ rated devices. Different temperature-dependent electrical parameters were identified and measured for a number of devices. The influence of spread in measured parameters was investigated experimentally during avalanche breakdown transient switching events and important findings have been highlighted

Experimental demonstration of an optimised PWM scheme for more even device electro-thermal stress in a 3-Level ANPC GaN inverter

GaN device as one potential power electronics device has been gained much attention recently. One of the power conversion systems, ANPC inverter using GaN HEMT is potentially considered to be prospective usage of low loss and high efficiency. In this work, we demonstrate one optimised PWM scheme aims at balancing the device electro-thermal stress based on Parma PWM to control 3-Level ANPC GaN inverter. The method is to decrease the loss for switches account for the large loss and increase the loss for switches with less thermal stress initially. The simulation and experimental results prove the effectiveness of the optimised PWM in controlling the loss distribution

Modeling environmental ageing in masonry strengthened with composites

The effects of environmental ageing due to rising damp and salt crystallization on composite strengthening systems, e.g. fiber reinforced polymer (FRP) and fiber reinforced cementitious matrix (FRCM), bonded to masonry substrates are still scarcely known. Although few laboratory tests have been recently conducted to this aim, very limited information is available. In this paper, the simulation of accelerated weathering/ageing cycles of masonry strengthened with composites is proposed by means of a multiphase model which accounts for salt transport and crystallization. This multiphase model is implemented together with ad hoc boundary conditions and a restart analysis procedure which attempt to reproduce the repetition of weathering cycles (composed of a wetting phase in a saline solution and a drying phase in the oven). Laboratory accelerated weathering tests on masonry specimens strengthened with lime mortar-based FRCM are numerically reproduced. Additional information on the salt crystallization process within the specimen is obtained along with the weathering procedure. Further numerical insights are shown and compared for different strengthening systems, i.e. cement mortar-based FRCM and FRP. Different salt crystallization patterns in the specimens with different strengthening systems are observed and discussed

SiC power MOSFETs performance, robustness and technology maturity

Relatively recently, SiC power MOSFETs have transitioned from being a research exercise to becoming an industrial reality. The potential benefits that can be drawn from this technology in the electrical energy conversion domain have been amply discussed and partly demonstrated. Before their widespread use in the field, the transistors need to be thoroughly investigated and later validated for robustness and longer term stability and reliability. This paper proposes a review of commercial SiC power MOSFETs state-of-the-art characteristics and discusses trends and needs for further technology improvements, as well as device design and engineering advancements to meet the increasing demands of power electronics

A Method for Battery Sizing in Parallel P4 Mild Hybrid Electric Vehicles

This article deals with a sensitivity analysis concerning the influence that the capacity of the battery in a parallel hybrid powertrain has on the vehicle's energy regeneration. The architecture under analysis is constituted by an internal combustion engine (ICE), which provides traction to the front axle's wheels, and an electric motor powering the rear wheels. The energy management system (EMS) is based on a simple torque split strategy that distributes the driver's required torque between the front and rear machines as a function of battery and electric motor functional limitations (state of charge, temperatures, and maximum admissible currents). Together with the selected driving cycles, the central role played by the battery size in the overall vehicle recoverable energy is evaluated, while the influence of the powertrain limitations is highlighted, accounting both for uncertain parameters (e.g., initial state of charge [SoC 0]) and for tunable parameters (e.g., maximum electric traction vehicle speed). Therefore, a method of sizing the battery of a P4 mild hybrid electric vehicle (HEV), which allows the maximization of the braking energy recovery, is developed

High temperature pulsed-gate robustness testing of SiC power MOSFETs

© 2015 Elsevier Ltd. Silicon Carbide (SiC) gate oxide reliability still remains a crucial issue and is amongst the important consideration factors when it comes to the implementation of SiC MOS-based devices within industrial power electronic applications. Recent studies have emerged assessing the gate oxide reliability of SiC MOSFETs. Such studies are needed in order to fully understand the properties of SiC/SiO2 interface which is currently holding back the industry from fully utilising the superior features that SiC may offer. This paper aims to present experimental results showing the threshold voltage (VTH) and gate leakage current (IGSS) behaviour of SiC MOSFETs when subjected to pulsed-gate switching bias and drain-source bias stress at high temperature over time. The results obtained are then used to investigate the gate-oxide reliability of SiC MOSFETs. 2D TCAD static simulation results showing electric field distribution near the SiC/SiO2 interface are also presented in this paper

Numerical modelling-based damage diagnostics in cultural heritage structures

In this paper, a numerical modelling-based damage diagnostics methodology is proposed for cultural heritage structures (CHSs) made of masonry. Firstly, an integration of 3D documentation data (i.e. point clouds and virtual tours) is developed for the rapid numerical model generation of CHSs. This allows to directly exploit non-comprehensive point clouds (e.g., associated to outer surfaces only) for the solid finite element model generation, where the lacking information is merged with off-site interactive and immersive frameworks. Secondly, a number of nonlinear static and dynamic analyses are conducted on the generated solid model to account for various load scenarios (e.g., earthquakes, soil settlements, etc.), considering a nonlinear continuum constitutive law. Thirdly, a crack pattern matching indicator is introduced to quantitatively identify the most likely load scenario which originated the damage pattern present in the CHS, by comparing numerical and actual crack patterns. The proposed methodology allows to rapidly generate and extract the numerical model that reflects the current (damaged) state of the CHS. This also allows to identify the parts of the CHS susceptible to further damage. The effectiveness of the proposed methodology is promisingly assessed on an actual historical masonry structure, the Morris Island lighthouse in South Carolina (USA)