Large domain YBa2Cu3O7-d/Y2BaCuO5 (YBCO) samples were prepared by top-seeded melt-textured process, with the addition of SnO2 and CeO2 or PtO2. In comparison to that in the CeO2-doped sample, the ...YBa2Cu3O7-d (123) matrix was twisted in the PtO2-doped sample, and its Y2BaCuO5 (211) particles were larger on average and less homogeneously distributed. The PtO2-doped sample showed a more obvious second-peak effect and higher values of a-b plane critical current density (Jabc) and irreversibility fields. Enhancement of Jabc is related to microstructure inhomogeneity and core surface pinning. 8 refs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
New types of electrical motors based on bulk high temperature superconductors (HTS) are presented. Theoretical and experimental research of these motors is described. Results for a series of 100, ...300, 500 and 1000 W HTS motors with cylindrical and disk rotors are presented. It is shown that, at liquid nitrogen temperatures, the specific mass-dimension parameter of hysteresis HTS machines is 5–7 times better than for the conventional hysteresis machines.
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Several hysteresis motors have been constructed with an output power up to 500 W at T=77 K. The rotors of these machines consist of melt-textured YBCO. In this work, the authors present detailed ...investigations on the magnetic processes in these rotors. Spheres were cut from melt-textured YBCO and investigated by rotating in vector-VSM. From these measurements, torque moments on the sample, hysteretic losses and the slip between external field and the sample can be calculated. The same dependence of the output power on the magnetic field for the samples as for the constructed motors can be derived. Influences of the critical current density and the domain size can be separated by changing the temperature.
High-temperature melt-textured material prepared in a batch process with reproducible material parameters and properties can be used successfully to construct electromotors with an increased energy ...and force density. A production process with high efficiency and moderate costs is the basis for the technical application of bulk melt-textured yttrium-barium-copper-oxide. The increased production rate also demands adequate characterization techniques that have to provide the material prarameters needed for the specific application. The most suitable characterization technique has to be chosen for routine characterization. In this article, measurements were performed to simulate magnetic processes in electromotors. Functional models running in liquid nitrogen were constructed.
A superconducting/electromagnetic hybrid bearing has been designed using active radial electromagnetic positioning and a superconducting passive axial levitator. This bearing has been tested for an ...induction machine with a vertical shaft. The prototype was conceived as a four-pole, two-phase induction machine using specially designed stator windings for delivering torque and radial positioning simultaneously. The radial bearing uses four eddy-current sensors, displaced 90 degree from each other, for measuring the shaft position and a PID control system for feeding back the currents. The stator windings have been adapted from the ones of a standard induction motor. The superconducting axial bearing has been assembled with commercial NdFeB permanent magnets and a set of seven top-seeded-melt-textured YBCO large-grain cylindrical blocks. The bearing set-up was previously simulated by a finite element method for different permanent magnet-superconductor block configurations. The stiffness of the superconducting axial bearing has been investigated by measuring by a dynamic method the vertical and transversal elastic constants for different field cooling processes. The resulting elastic constants show a linear dependence on the air gap, i.e. the clearance between the permanent magnet assembly and the set of superconducting large-grain blocks, which is dependent on cooling distance.
A superconducting passive axial bearing has been developed for an induction machine with vertical rotor and two active radial magnetic bearings, resulting in a fully levitating system. This prototype ...has been designed on the basis of a previous one reported by Salazar-Stephan as a 4-pole 2-phase induction machine using windings of a standard motor. Each active radial bearing measures four shaft-positions using eddy-current sensors, each displaced by 90 degrees. The levitation has been performed using two NdFeB permanent magnets and bulk pieces of seeded-melt-textured YBCO. The YBCO pieces have been characterized by measuring the levitation forces and mapping the remanent magnetic field with Hall probes. The radial stability of the system is modeled and discussed.
A superconducting/electromagnetic hybrid bearing system is currently under development and test. This system consists of a thrust superconducting magnetic bearing and a double radial active ...electromagnetic bearing/motor devices. The thrust bearing has been designed using NdFeB permanent magnets levitating on a set of superconducting monoliths of YBCO, prepared by top seeded melt texturing technique, which supports the weight of the rotor. The bearing/motor devices were conceived as 4-pole 2-phase induction machine using stator windings for delivering torque and radial positioning simultaneously. Using this superconducting axial bearing and the active bearings for the rotor radial positioning, a fully levitating vertical-shaft inductive machine has been tested. The tests were successful in reaching a controlled levitation up to 6,300 rpm.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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