Superconductors for Electrical Engineering.

With the development of more and more performant superconducting conductors (critical current density, losses, stability, critical field. . . ) we are now entering a new era in electrotechnology (constant and slowly varying conditions since the 70's and alternating conditions tomorrow). The aim of this paper is to throw some light on the essential questions raised by the designing of cryogenic machines. After a review of superconductivity, we investigate the thermoelectromagnetic characteristics of a conductor from the point of view of its losses, stability and construction. Finally we classify three principal types of conductors according to the desired application (constant, alternating and alternating normal-superconducting conditions).