A Review of Technology Readiness Levels for Superconducting Electric Machinery

Superconducting electric machines (SEMs) have the potential to be commercially available in the coming years. This commercialization depends on the availability of high-temperature superconductors (HTS) produced on a large scale. HTSs have high current densities and low losses, making them the leading technology choice for future light and compact high-power-density superconducting rotating machines, with a particular niche for high torque at low frequency. The advantages of SEM in its fully superconducting design or hybrid configuration (conventional stator, superconducting rotor) inherit from the characteristics of the superconductor material. So, they can show greater efficiency at a higher power density and lighter frame than their conventional counterparts for an equivalent power rating. Applications like electric aircraft, naval propulsion, and wind turbines, among others, are likely to use SEMs if the rated power has to be increased beyond what is technically available with conventional technology. In this context, this paper reviews SEMs and their applications. However, it also aims to highlight the main the literature projects with a minimal Technology Readiness Level (TRL) larger than three. Due to the diversity of the superconductors’ characteristics and the variety of machines, the modes of operation of SEMs can be quite distinct from conventional machines. Taking into account such diversity, SEMs are presented and sorted out by their operational principles and the choice of superconducting material. Finally, the future perspectives of SEM are discussed.