ELECTRICAL TESTS ON A FULLY SUPERCONDUCTING SYNCHRONOUS MACHINE

The emergence in the eighties of the ultra fine multifilamentary superconducting wires with very low losses under varying magnetic fields has allowed the tests in 1987 of a three phase 50 Hz superconducting stationary winding with a classical copper/iron rotor. A superconducting field rotor has been constructed and mounted into the previous stator to form a fully superconducting machine. The rotating part becomes rather simple: a Helium vessel rotates into low pressure vessel to avoid thermal losses by turbulence. There is no thermal shielding due to the cryogenic environment of the stator and the electromagnetic shield, present in "classical" superconducting generators, has been avoided with the low loss superconductors used. The combined 900 mm long, 320 mm in diameter, rotor-stator cryostat uses fiber-glass composites in the central parts due to the rotating fields under permanent or transient operations. This article reports the first electrical tests of this small scale 18 kVA machine under permanent and sudden short circuit tests.