APPLICATION OF 50 HZ SUPERCONDUCTORS CLOSE TO SELF-FIELD CONDITIONS

Applications of 50 Hz superconductors like the transformer and the fau lt current limiter correspond to relatively low magnetic fields, so th at AC losses and stability are mainly governed by the conductor self f ield. AC loss calculations as they are performed in most cases for sup erconductors, are based on the Bean critical state model which states that everywhere in a superconductor, the current density has a modulus equal the critical current density J(c). This model is applicable whe n the superconducting transition E(J) is very sharp, but sizeable disc repancies appear for 50 Hz superconductors, as they present a relative ly smooth superconducting transition. AC loss calculations have been d eveloped using the Maxwell equations combined with the actual E(J) rel ationship. The heat generation in the conductor is then used as an inp ut for a numerical, calculation of the temperature distribution throug h the superconductor. The stability limits directly derive from the th ermal model.