Showing papers by "Pascal Bevilacqua published in 2015"

Accelerated Ageing of Metallized Film Capacitors Under High Ripple Currents Combined With a DC Voltage

Abstract: In view of their potential for high dielectric breakdown strengths, low dissipation factors, and good dielectric stability over a wide range of frequencies and temperature, metallized films capacitors are very used components for aeronautic applications Nevertheless, capacitors remain unreliable components; a good acquaintance of their deterioration over time would enable us to perform a predictive maintenance on the component and thus improve the availability of the whole system This operation requires the knowledge of the capacitor ageing law and their failure mechanisms associated with the application In a standard six pulses rectifier-fed pulse width modulation inverter, dc-link capacitors are generally subjected to gradients of temperature due to the encountered electrical stresses Since traditional floating ageing tests, which consist on applying constant voltages and temperature across the component, do not reflect the normal ageing of the component, we propose in this paper to study the degradation kinetics of metallized films capacitors under high ripple currents, alone or combined with a dc voltage across the devices terminals It will therefore reproduce with a more representative way the ageing of the component in comparison with the traditional floating ageing tests Based on the resonant circuit properties, the ageing test bench especially developed for our study provides high currents and voltages from a low power source Through the study and analysis of the capacitors parameters evolution under high ripple currents, an original ageing law is proposed to model the capacitance decrease with time based on the electrochemical corrosion of the capacitors electrodes The adequacy between the experimental points and the model proved the validity of the proposed law

Temperature Dependence of 4H-SiC Ionization Rates Using Optical Beam Induced Current

Abstract: The behavior of 4H-SiC power devices in severe environment with varying temperature is a key characteristic indicating their reliability. This paper shows the dependence of the ionization rates of 4H-SiC with respect to temperature. Optical Beam Induced Current (OBIC) measurements have been performed on PN junctions to determine the multiplication coefficient for temperature varying between 100 and 450K. That allows extracting the ionization rates by fitting the curves of multiplication coefficient.

Investigation of Using SiC MOSFET for High Temperature Applications

Abstract: This paper presents the performances expected by SiC MOSFETs for high temperature applications. A complete static and dynamic electrical characterization of SiC MOSFETs have been tested under varying temperature from 25°C to 250°C using suitable packaging materials. To go further, aging tests have been performed to evaluate lifetime of SiC MOSFET under switching condition up to 300°C.

Lifetime of holes determination in 4H-SiC using two-photon optical beam induced current method

Abstract: Wide bandgap semiconductors such as silicon carbide, gallium nitride and diamond have been recently investigated in order to replace silicon in the power electronic domain. In this paper, silicon carbide devices are studied using an optical method. It consists on illuminating a reverse biased junction with a laser beam with an appropriate wavelength, and then measuring the induced current due to the photon absorption. According to the wavelength, one- or two-photon absorption is triggered when photon energy is respectively higher or lower than the semiconductor bandgap. In the latter case, the probability of electron hole pair (EHP) generation is very small, which leads to use a powerful incident beam. In this paper, two-photon generation is used in order to determine the lifetime of minority charge carriers in N doped 4H-SiC. The incident beam is a pulsed green source with a wavelength of 532 nm and a high power density that can reach up to 6 GW.cm−2. Test devices are PN diodes protected by a junction termination extension (JTE). Results show a hole's lifetime of 730 ns.

2D Electric field imagery in 4H-SiC power diodes using OBIC technique

Abstract: Wide band gap semiconductors are more and more used, especially to design high voltage devices. However, some devices show lower breakdown voltages than those predicted in theory. These early breakdown are in general due to imperfections in the peripheral protections of the active junction. The aim of these protections is to reduce electric field peaks at the periphery of the junction. Thus, it is important to study the electric field distribution on the device periphery to detect any protection weakness. This paper presents a 2D electric field imagery using OBIC (optical beam induced current) technique. 2D cartographies are realized on JTE (junction termination extension) protected diodes in order to display electric field on diode peripheries. Other measurements are also performed on circular avalanche diodes protected with a MESA etching and provided with optical window. In both cases, OBIC techniques is demonstrated to be an efficient method to obtain electric field distribution within the device and to locate defects.