High temperature superconducting rotating electrical machines: An overview

Superconducting rotating machines are more efficient, smaller and lighter than conventional ones. Thus, they can reduce energy consumption and can be an enabling technology in applications that require light-weight machines. Using high temperature superconducting (HTS) materials in machines simplifies cooling designs compared to using low temperature superconductors. This review presents a summary of all major HTS machines built worldwide in the 21st century, covering several different types of machines, e.g., synchronous, induction, dc homopolar, ac homopolar, reluctance, hysteresis and flux modulation machines. A classification of the machines is also described based on the form of superconductor used: wires/tapes, bulks and stacked tapes. The working principles of the more unusual HTS machine types are qualitatively explained, such as machines with claw poles, dc and ac homopolar machines, magnetic gears, vernier permanent magnet machines and flux switching dc machines. Finally, the targeted, practical applications of HTS machines are explored and the significant trends and challenges in HTS machine design in recent years – and in the future – are described.