First Conclusions on the Advantages of Full Superconducting Synchronous Machines

The development of superconducting (SC) wires with reduced losses under ac magnetic fields allows the design of ac machines with superconducting coils for both field and armature windings. Cryogenerators using SC field winding have been an exciting field of applied research in the last twenty years and the results have been good enough to design and build some industrial size units. High specific power, reduced losses and better comportment during transients were the major advantages of this type of machines. In the case of full SC synchronous machines, a preliminary study shows that these advantages are enhanced (power density is increased by a factor of 3, armature losses are reduced). However the synchronous reactances will be higher than for previous cryogenerators, reducing mechanical stresses and the general design will become simplified, These first conclusions are attractive enough to foresee the construction of a 20 kVA ac generator to prove its feasibility.