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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.

Abstract This letter presents a circuit for powering cascode gate driver circuits with super‐junction (SJ) MOSFETs in a bridge‐leg. The cascode gate driver gives inherent MOSFET intrinsic diode deactivation, and the bridge‐leg incorporates an inductive turn‐on snubber which controls the charging currents into the MOSFETs’ output capacitances. The cascode driver circuits and snubber inductor are configured such that the gate‐drive energy is derived from the power stage.

This paper reports a pioneering demonstration platform of a cryogenic propulsion unit at liquid nitrogen temperature. A high temperature superconducting (HTS) machine is connected with a cryogenic power rectifier in a generator mode to prove the feasibility of a cryogenic propulsion unit for electric aircraft propulsion applications. Machine operation was carried out with a special focus on the total heat dissipation inside the HTS AC windings. Different types of 2G HTS tapes were tested to provided data for stator coils’ design. The transient operation was carried out to represent a short-circuit failure in one of the power electronic devices. The test shows AC loss performance of the HTS windings using calorimetric method during the short circuit event, indicating the importance of developing protection schemes for the cryogenic propulsion units to prevent damage to the HTS components. The paper provides initial insights into the interaction between superconducting machines and cryogenic power electronics within a cryogenic propulsion unit. It is an important first step to understand and further develop cryogenic propulsion technology for future electric aircraft.

This article presents a gate driver circuit with all-magnetic isolation for driving silicon carbide (SiC) power devices in a three-level T-type bridge-leg. Gate driver circuitry for SiC devices has to be tolerant of rapid common-mode voltage changes. With respect to the resultant potentially problematic common-mode current paths, an arrangement of transformers is proposed for supplying the power devices with drive signals and power for their local floating gate driver circuits. The high-frequency carrier phase-switching technique is used to reduce the number of transformers. Signal timing and other implementation issues are addressed when using this arrangement with the T-type converter. The circuit is demonstrated in a 540 V bridge-leg constructed around 650 V and 1200 V cascode-connected normally-on SiC junction field effect transistors (JFETs).

This study compares simple conventional and cascode driver circuits for the SiC bipolar junction transistor (BJT). A low-voltage silicon metal-oxide-semiconductor field-effect transistor is used in the emitter of the BJT to realise the cascode variant. The circuits are experimentally evaluated when switching a current of 2.5 A and a voltage of 600 V in a buck converter.

A single-stage 600 : 1 ratio voltage step-down dc–dc converter designed to produce a voltage of between 1 and 1.5 V from a rectified single/three-phase AC supply, for application in a desalination process, is presented. A coupled-inductor design is used, and a novel snubber circuit with energy recovery manages the effects of imperfect coupling (leakage) between the coupled windings. The circuit, which is bidirectional, allows for the power devices to be rated for either high current or high voltage. This presents significant cost and performance advantages compared to a conventional single-stage buck converter where such a large step-down ratio would require a small duty ratio and components with high ratings for both voltage and current: in this case, ratings of 1200 V to withstand input dc voltage switching, and 1000 A to deliver the output current, would be required.