Tabea Arndt

Superconducting Properties of Thick Films on Hastelloy Prepared by the Aerosol Deposition Method With Ex Situ MgB2 Powder

We present a new high-deposition-rate coating technique that allows us to produce at room temperature long thick films of MgB₂ on flexible steel substrates. Such a technique might give rise to new tapes with higher filling factors compared to the standard processed tapes. With the so-called aerosol deposition technique, MgB₂ films were prepared on Hastelloy substrates with commercially available <italic>ex situ</italic>-prepared MgB ₂ powder (<italic>T</italic>_C,onset of 38 K, <italic>J</italic>_C of 3.8·10³ A/cm² at 4 K and 1 T). Microscopic analyses yield nanocrystalline dense films with high film stresses. The as-deposited films have so far a superconducting transition temperature <italic>T</italic>_C0 of 18.1 K and a critical current density <italic>J</italic>_C up to 5·10³ A/cm² at 4 K and self-field obtained.

Design and Development of a Test Rig for HTS Generator Components

High temperature superconducting (HTS) rotating machines show several significant advantages compared to machines built in conventional technique. Former experiments on rotating electric synchronous machines like motors and generators in the power range up to several MW confirmed the well-known benefits of HTS machines like smaller size, less weight and last but not least, a significantly increased efficiency. Especially the increased efficiency of large HTS-Generators up to several hundreds of MW-as operated by utilities-promises an efficient use of fuel and energy sources. This will allow reduced carbon dioxide emissions and becomes more and more important. The development of HTS rotor technology for generators in the range of hundreds of MW bears new challenges. HTS generator windings capable to withstand large centrifugal forces and carrying large currents are required. Also a special cooling system for the rotating winding and further components with novel design will be necessary and have to be developed. In a future HTS generator based on such components, these will have to operate very reliably, so a facility is needed to be able to perform tests. Therefore it is essential to design and build a specific test rig for investigation and test of the required new components. The present paper deals with design and development of such a test rig that allows component tests under realistic conditions, using radii in the range of 0.45 m as in a generator application at rotational speed of up to 3000 rpm, and at low operating temperatures of about 30 K. Additionally a 3 kA high current power supply for HTS test objects like coils or contacts is projected. Aspects of rotor dynamics and fatigue strength analysis had to be considered.

Aspects on HTS applications in confined power grids

In an increasing number of electric power grids the share of distributed energy generation is also increasing. The grids have to cope with a considerable change of power flow, which has an impact on the optimum topology of the grids and sub-grids (high-voltage, medium-voltage and low-voltage sub-grids) and the size of quasi-autonomous grid sections. Furthermore the stability of grids is influenced by its size. Thus special benefits of HTS applications in the power grid might become most visible in confined power grids.