Design of superconducting magnets for power applications

A three-year research project, called DRYSMES4GRID, was recently funded by the Italian Minister of Economic Development, Italy. The project is aimed to demonstrate the feasibility of cost-competitive SMES based on magnesium diboride (MgB2) with a cryogen-free cooling by means of the manufacturing and the testing of a demonstrator with an objective rating of 500 kJ/200 kW. The preliminary design, concerning the definition the geometry of the coil and the reference MgB2 conductor based on the functional requirements of the system, is first discussed. The detailed design of the coil, aimed at producing the information and the technical drawings needed for the manufacturing of the coil, is then presented. The mechanical behavior of the coil during cool down and successive energization up to the nominal transport current is analyzed and the compatibility of stress and strain with allowable limits of the conductor is verified. The distribution of electrical stress on the coil during the switching of the power electronic converters is also calculated for the proper design of electrical insulation. Results of quench analysis are also presented showing that the maximum hot spot temperature reached when the coil is discharged is within the design value. Evaluation of the thermal load due to radiation, conduction through the supports, current leads and AC loss is presented. The same methodology has been applied on another superconducting application in order to design the SC coil of a Saturated Iron superconductive Fault Current Limiter (SI-SFCL) at Changwon National University, South Korea. The SI-SFCL consists of three main parts: one magnetic iron-core, one normal conductive primary coil (CPC), and one superconducting secondary coil (SSC). The design of the SSC was based on the terms of shape, wire types, required fault current limit and protection aspects.