Reliability is a fundamental requirement in electric propulsion systems, involving a particular approach in studies on system failure probabilities. An intrinsic improvement to the propulsion system involves introducing robust architectures such as fault-tolerant motor drives to these systems. Considering the potential for hardware failures, a fault-tolerant design approach will achieve reliability objectives without recourse to optimized redundancy or over-sizing the system. Provisions for planned degraded modes of operation are designed to operate the motor in fault-tolerant mode, which makes them different from the pure design redundancy approach. This article presents how a five-phase permanent-magnet synchronous motor operates under one- or two-phase faults, and how the system reconfigures post-fault motor currents to meet the torque and speed requirement of reliable operation that meets the requirements of an electric propulsion system.

High-temperature superconducting (HTS) magnets have found wide applications in high-field settings owing to their high current capabilities. Typically, these magnets are powered by high-current power supplies via current leads, which can complicate insulation between cryogenic and room temperature environments. However, new developments in flux pumps for HTS magnets have enabled charging of kA levels of current without power supplies. By combining flux pumps with HTS persistent current operation, it is possible to achieve accurate flux modulation and eliminate the need for power supplies and current leads. In this study, we report on a novel feedback-controlled flux modulation for HTS magnets in persistent current operations. This flux modulation is based on a flux pump mechanism that generates a DC voltage across the charging superconductor by applying a current higher than its critical current. With closed-loop feedback control, our flux modulation can achieve precise injection and reduction of HTS magnet current in increments of 0.5 A. This technology can lead to stable magnetic fields in HTS magnet designs. We anticipate that this work will enable future magnets to operate in a stable persistent current mode within a closed cryogenic chamber, significantly reducing the footprint and power demand of HTS magnets and opening up new opportunities for their applications.

High-temperature superconducting (HTS) flux pump is a promising way of energizing superconducting magnets without direct electrical contacts. It can remove the resistive heating and heat leakage from the current leads at room temperature. It is well known that applying the current over the critical current of the superconductor will force the superconducting layer to enter into the flux flow regime. This flux flow resistivity generates a dc voltage across the length of the HTS tape. This phenomenon is well understood; however, it is difficult to generate a high dc charging voltage without a high current. In this article, we demonstrate a novel flux pumping technique by using a noninductive bifilar bridge wound in parallel to the HTS coil. This configuration can generate large dc voltages using relatively small currents. It results in effectively pumping dc currents equal to the critical current for large HTS magnets.

To reduce emissions from the aviation industry and meet the targets set by different countries, research has been focused on investigating all-electric aircraft. To make this vision practical, superconducting machines are expected to power the propellers, as they are half the size and a third the weight of conventional machines. The main purpose of this paper is to do a higher-level study of a reliable holistic protection system for all-electric aircraft; that can reduce heat leakage and be able to detect faults reliably. Thus, three main protection systems were investigated; 1) cryogenic voltage source converter superconducting magnetic energy storage system (VSC-SMES), 2) cryogenic dc breaker integrated with superconducting fault current limiter (SFCL), and 3) machine learning algorithm for fault detection. By immersing the protection system at cryogenic temperature, the paper has shown that passive leakage can be eliminated, and thus more energy can be saved for the fuel cell. The paper has also demonstrated that using machine learning for the SFCL-dc-breaker system can consistently eliminate faults and protect the system.

High-temperature superconducting (HTS) magnets are widely used in high field applications due to their exceptional current-carrying capabilities. Traditionally, these magnets are powered by high current power supplies via current leads, which complicates insulation between cryogenic and room temperature environments and introduces significant heat leaks. Recent advancements in flux pumps for HTS magnets now allow charging currents in the kA range without the need for traditional power supplies. However, while some research has realized conduction-cooled traveling wave HTS flux pumps, much of the focus for transformer rectifier flux pumps remains on operating them to charge magnets at liquid cryogen temperatures, with limited attention given to the heat load and cooling capabilities of modern dry cryocoolers. This study presents a compact, modular flux pump designed for operation in conduction-cooled environments. It examines the impact of cooling power on the flux pump’s performance in such settings. A lumped element model implemented in PLECS is validated through experiments conducted at 70 K and 30 K, demonstrating consistent results. Based on this validation, we demonstrate the capability to charge an HTS magnet to 300 mT ( ≈ 800 A) in a conduction-cooled environment using a compact, self-regulating HTS flux pump.