1. Context

The application of superconductors to electrical power devices goes back a long way. It dates back to the 1960s, when the first "usable" superconductors - i.e. those capable of carrying high currents under magnetic inductions - were developed. The first superconducting electric machine went into operation in 1965.

Superconductors may seem like the ideal material for electrical equipment designers. The much higher current densities (factor 10 to 100) in superconductors compared with copper, and the absence of Joule losses, point to quantum leaps in mass and volume performance associated with exceptional efficiencies. Superconductors also provide new functions, inaccessible to conventional techniques, such as energy storage in a short-circuited superconducting coil. Table