Is an antiparallel SiC-Schottky diode necessary? Calorimetric analysis of SiC-MOSFETS switching behavior

Within this paper the switching losses of a Wolfspeed 25mOhm bare die SiC-MOSFET are measured in a hard switching 800 V DCDC-converter with five different commutation partners. A small and a large SiC Schottky diode, an SiC-MOSFET body diode and a combination of body and Schottky diode are compared at different switching speeds and switching currents. The results show quite well the reverse recovery charge dependence of SiC-MOSFET's body diode on switching speed. In contrast to common electric measurements where losses are calculated, the calorimetric measurements reveal exactly what shall be quantified: The temperature rise of the switching MOSFET

Non-isolating DC/DC converter for a fuel cell powered aircraft

Fuel cells in aircraft applications are gaining more and more interest because of higher possible efficiency and increasing air pollution standards. A necessary supplement is an efficient, lightweight and reliable DC/DC-converter to adjust the weak fuel cell characteristic to the voltage level of buffer batteries and drive inverters. Cosmic radiation, condensation, strict EMI-limits and significantly increased creepage distances impair a light and efficient converter. This paper explains approaches to solve those technical difficulties, especially a way to fulfill EMI standards without a large and heavy EMI-filter and introduces the first converter's application, a fuel cell powered UAV. The converter is developed with a strictly scalable design. Therefore an up-rating to multi megawatt applications for larger aircraft is discussed and possible occurring challenges are evaluated

A 3.6 kV full SiC fuel cell boost converter for high power electric aircraft

In order to electrify commercial passenger aircrafts with several MW propulsion power, voltages in the kilovolt range are necessary. Since fuel cells show a soft output voltage characteristic, a boost converter is essential. Within this paper a 3.6 kV fuel cell DCDC-converter is presented that is based on 3.3 kV SiC-MOSFETs allowing much higher light load efficiency and switching frequency than conventional silicon IGBT solutions. The higher light load efficiency is an important feature for long haul aircrafts since the maximum power is only needed for take-off and climbing up to the cruising altitude. Within this paper, a single phase setup is built-up, the electrical design is explained and efficiency measurements are performed

Western Star, 1913-04-09

The Western Star began publication on Newfoundland's west coast on 4 April 1900, appearing weekly with brief semiweekly periods up to 1952, when it became a daily. As of 17 April 2019 it continues as a free weekly community paper