Mars Express/ASPERA-3/NPI and IMAGE/LENA observations of energetic neutral atoms in Earth and Mars orbit

The low energy neutral atom imagers on Mars Express and IMAGE have revealed that the neutral atom populations in interplanetary space come from a variety of sources and challenge our current understanding of heliospheric physics. For example, both in cruise phase and at Mars, the neutral particle instrument NPD on Mars Express observed "unexplained neutral beams" unrelated to Mars which appear to be either of heliospheric or solar wind origin. Likewise, the NPI instrument on Mars Express has revealed streams of neutral atoms with different properties than those observed by NPD. Independently, IMAGE/LENA has reported neutral atom observations that may be interpreted as a "secondary stream" having different characteristics and flowing from a higher ecliptic longitude than the nominal upstream direction. Both sets of observations do not appear to fit in easily with the neutral atom environment from 1.0-1.57 AU as it is currently understood. In this paper we examine some highly suggestive similarities in the IMAGE/LENA and Mars Express/ASPERA-3/NPI data to try to determine potential origins for the observed signal.Comment: in press Adv. Sp. Res., 15 pages, 9 figure

COSIVU - Compact, Smart and Reliable Drive Unit for Commercial Electric Vehicles

The EU-funded FP7 project COSIVU [1] aims at a new system architecture for drive-trains by development of a smart, compact and durable single-wheel drive unit with integrated electric motor, compact transmission, full silicon carbide (SiC) power electronics (switches and diodes), and an advanced ultra-compact cooling solution. The main goals of COSIVU is to increase performance, flexibility as well as safety and reliability of commercial hybrid and electric vehicles, which are even more demanding with respect to power, performance, durability [2], and availability than other types of vehicles. In addition, the new architecture will be adapted to other vehicle platforms such as passenger cars. The COSIVU solution is integration of the wheel motor and the inverter into one system package. During the first twelve months of the project the COSIVU system architecture concept has been developed and a highly modular packaging concept was chosen for the power stage, using "Inverter Building Blocks" (IBB). SiC bipolar transistors and diodes have been selected and production of packaged SiC devices has started. The design of a double sided cooling version of the modules has been initiated. A theoretical design of a new driver solution, which includes power saving and reliability enhancing features, has been done. A thermal investigation test bench has been designed for the thermal characterization of the SiC based power modules

Microshutters for MEMS-based time-of-flight measurements in space

This paper reports on the fabrication, integration and first operation of a mechanical microshutter in a time-of-flight (TOF) based ion detector in space. The microshutter is fabricated from a silicon on insulator (SOI) wafer and operated in a resonance mode, 306 kHz. Open time of the shutter is 100 ns. The microshutters are integrated in the PRIMA instrument, which is part of the payload on the Swedish PRISMA mission. PRISMA was successfully launched into low Earth orbit on June 15, 2010

Reliability of new SiC BJT power modules for fully electric vehicles

Wide-bandgap semiconductors such as silicon carbide (SiC) or gallium nitride (GaN) have the potential to considerably enhance the energy efficiency and to reduce the weight of power electronic systems in electric vehicles due to their improved electrical and thermal properties in comparison to silicon based solutions. In this paper, a novel SiC based power module will be introduced, which is going to be integrated into a currently developed drive-train system for electric commercial vehicles. Increased requirements with respect to robustness and lifetime are typical for this application field. Therefore, reliability aspects such as lifetime-limiting factors, reliability assessment strategies as well as possible derived optimization measures will be the main focus of the described work

Reliability investigation on SiC BJT power module

In this paper reliability investigation results for a power module fully based on silicon carbide (SiC) devices are presented. The module comprises four SiC bipolar junction transistors (BJT) and four SiC diodes in half-bridge configuration and is part of a newly developed 3-phase inverter for construction vehicles as well as for passenger car applications. The reliability investigations include electro-thermal and thermo-mechanical finite element simulations as well as power cycling tests with subsequent failure analyses. Furthermore, a double-sided cooling approach for the SiC BJT power module will be described and its thermal performance compared to the single-sided cooling version

Modeling of SiC power modules with double sided cooling

Silicon Carbide (SiC) based transistor devices have demonstrated higher efficiency switching operation compared to silicon-based, state-of-the-art solutions due to the superior electrical and thermal properties of the SiC material. The improved current density and thermal conductivity allows SiC-based power modules to be smaller than their silicon counterparts for comparable current densities. The active chip area can be reduced further by effectively cooling the devices. In this work, a new power module including SiC bipolar junction transistors (BJT) and diodes and integrated double sided cooling will be introduced. The target application of these modules is a new drive-train system for commercial electric vehicles

Thermo-mechanical simulations of SiC power modules with single and double sided cooling

Effectively removing dissipated heat from the switching devices enables a higher current carrying capability per chip area ratio, thus leading to smaller or fewer devices for a given power requirement specification. Further, the use of SiC based devices has proven to increase the efficiency of the system thereby reducing the dissipated heat. Thermal models have been used to compare SiC power modules. Single and double sided cooling have been simulated. The simulated maximum temperatures were 141 °C for the single sided version and 119.7 °C for the double sided version. In addition, the reliability of a single sided module and thermally induced plastic strains of a double sided module have been investigated. A local model of the wire bond interface to the transistor metallization shows a 30/00 maximum increase in plastic strain during the power cycle. Simulations of the creep strain rates in the die attach solder layer for a power cycling loads also shows a 30/00 increase in creep strain per cycle