Characterizing Semiconductor Devices for All-Electric Aircraft

Cryogenic propulsion with hydrogen fuel cells replacing fossil fuels is a promising solution to cut carbon emissions in the aviation sector. Hydrogen will also be used for cooling the superconducting machines and power converter circuits. This article aims to test devices suitable for power electronic converters supplying a 1.6 MW superconducting machine. SiC MOSFET and Si IGBT modules with ratings of 1200 V and more than 450 A are selected to assess their performance at different temperatures. Four tests are conducted to determine: 1) the forward voltage drop, 2) the breakdown voltage, 3) the switching behavior, and 4) their operation with two modules in parallel. A bespoke current sensing rig has been developed that avoids the need to extend conductors outside the cryogenic zone in the switching losses measurement test. This configuration introduces minimal stray inductance into the circuit, which minimizes errors in the measurement. One of the aims of this article is to assess the suitability of different module technologies for SiC MOSFET and Si IGBTs in cryogenic applications. Six power modules (SiC MOSFETs and Si IGBTs) were evaluated at both room and cryogenic temperatures. Three of the modules employed conventional bond wire technology, while the other three utilized solid cover (SLC) technology that has no internal bond wires. It was found that the modules which employed SLC technology were the only ones able to survive the extreme temperatures. Following this, a comparison was made between the energy losses of the three SLC modules (two Si IGBTs and one SiC MOSFET) that were able to withstand low temperatures. The results indicated that the performance of the SiC MOSFET module worsens at cryogenic temperatures, whereas the performance of the Si IGBT modules improves with decreasing temperatures. Finally, an inverter simulation was conducted with each of the IGBT modules to estimate the efficiency.