Felipe Sass

Superconducting Levitation Using Coated Conductors

The second-generation (2G) YBCO wire has been used for several applications, such as electric power transmission and distribution cables, fault current limiters, MagLev vehicles, electric machines, high field magnets, superconducting magnetic energy storage, etc. The main advantages of 2G wires are: high critical current density values, large scale production, lower manufacturing cost than first generation, and superior performance under high magnetic fields. This work presents a preliminary study of superconducting magnetic bearings (SMB) using 2G wires as passive levitators. A superconducting block using stacked 2G wires was built to evaluate the behavior of coated conductors in the SMB application. The levitation and lateral force between the 2G block and a permanent magnet guideway was measured and compared with the results for an YBCO bulk with approximately the same dimensions. The results indicate that 2G wires have potential for applications with superconducting levitation, but its economic feasibility still depends on the coated conductors price decreasing.

Optimization of the Superconducting Linear Magnetic Bearing of a Maglev Vehicle

Considering the need for cost/performance prediction and optimization of superconducting maglev vehicles, we develop and validate here a 3D finite element model to simulate superconducting linear magnetic bearings. Then, we reduce the 3D model to a 2D model in order to decrease the computing time. This allows us to perform in a reasonable time a stochastic optimization considering the superconductor properties and the vehicle operation. We look for the permanent magnet guideway geometry that minimizes the cost and maximizes the lateral force during a displacement sequence, with a constraint on the minimum levitation force. The displacement sequence reproduces a regular maglev vehicle operation with both vertical and lateral movements. For the sake of comparison, our reference is the SupraTrans prototype bearing. The results of the optimization suggest that the bearing cost could be substantially reduced, while keeping the same performances as the initial design. Alternatively, the performances could be significantly improved for the same original cost.

Lateral Displacement Influence on the Levitation Force of YBCO Coated Conductor Linear Bearings

Superconducting coated conductors have been used for several large-scale applications. One potential application for YBCO second-generation (2G) wire is the development of superconducting magnetic bearings (SMB). The main advantages of 2G wires are large scale production, high critical current density values, lower manufacturing cost than first generation, and superior performance under high magnetic fields. This work proposes a study of a linear SMB using 2G wires as a passive levitator for MagLev vehicles. The 2G block is conceived to replace the YBCO bulk in the MagLevs SMB prototype, which is being built at Federal University of Rio de Janeiro. In this context, a superconducting block using stacked 2G wires was built to evaluate the behavior of this SMB. The forces between the 2G block and a permanent magnet were measured and compared with the results for an YBCO bulk with nearly the same dimensions. The experimental rig used for this work allows vertical and lateral displacements and a load cell is used to evaluate the SMB levitation force decay due to the lateral movement. The 2G block has presented lower force levels than ordinary YBCO bulks, but it presents potential to be applied in a SMB application.

Application of 2G-Tape for Passive and Controlled Superconducting Levitation

Second generation (2G) superconductor wires have been used for several applications. This work presents a preliminary study of superconducting magnetic bearings (SMB) using 2G wires. A double pancake superconducting coil (DPSC) was implemented to test the 2G wire in levitation technology. The coil was projected by simulations with the Finite Element Method (FEM). The 2G wire can be used for two types of SMB: linear (for MagLev vehicles), or rotational (for flywheels). In both applications the wire can be connected as a closed loop coil (for passive levitators), or as an opened coil (for applications where a controlled levitation gap is desired). A rotational SMB was made to investigate the levitation force between the DPSC and a permanent magnet cylinder showing promising potential of this application.

Persistent currents in a magnetic bearing with coated conductors

Superconducting magnetic bearings are normally built with bulk superconductors. Since coated conductors properties are far superior, we have proposed in a previous work the replacement of bulks for stacks of 2G wires in magnetic levitation devices. A major limitation of this replacement lies in the fact that the induced current is constrained in narrow loops along the available commercial widths of 2G wires. This work presents a technique to achieve wider loops of persistent current without the need of increasing the coated conductors width. As a result, the use of 2G wires in magnetic bearings took a step towards its economical feasibility.

Design and implementation of a digital control system for an axial flux switched reluctance motor

Nowadays, besides the rapid growth of different areas like the mechanical and electrical ones, it is possible to identify a particular effort to develop new motors including new electrical drives and control systems. Additionally, these equipments are being designed to give them the maximum efficiency as the energy cost is continuously increasing. With this in mind, some results related to a particular switched reluctance motor, are presented. The airgap between its poles are distributed in such a way that they are parallel to the rotation axis. Such structure is little studied by researchers. On the other hand, in order to maintain a low ripple torque, a particular algorithm is proposed which consists in imposing motor currents with a special format. The implementation of this strategy was made using two microcontrollers, one to determine the position and speed of the rotor while the second impose the appropriated current to the motor windings. This strategy has been successfully tested to control the speed of the rotor in a simple feedback loop.

Characterization of a Second Generation HTS Coil for Electrical Power Devices

Due to the electrical characteristics of second generation (2G) high temperature superconductor (HTS) wires, such as higher critical current density and superior performance than first generation (1G) HTS wire under magnetic fields, they have been chosen for use in the development of several superconducting devices for electric power applications. Since the majority of the electrical devices are designed using a conductor coil, it is necessary to understand the electrical characteristics of superconducting coils under different situations, to develop these equipment. An important aspect that should be considered in the project of 2G HTS coils is the influence of its self field. This effect could lead to a reduction in the 2G HTS wire critical current value resulting in damages due to heterogeneous quenching Therefore, this work aims the construction of a HTS coil using 2G wires, and the determination of its DC critical current under different conditions. The influence of the coil bending radius, by going to the minimum value recommended by the manufacturer, was also investigated. These measurements are essential for the development of electric power devices.

Proposal of a Novel Design for Linear Superconducting Motor Using 2G Tape Stacks

Plenary lecture given at the 8th Mid-European Clay Conference, held in Kosice (Slovakia) on July 4-8th, 2016.COST MOLIM WG3 Meeting, Algorithm Development and High-performance Computing in Chemistry and Physics; Bratislava, March 21-22, 2016; http://web4.umb.sk/molim2016/Oral presentation given at the 8th Mid-European Clay Conference, held in Kosice (Slovakia) on July 4-8th, 2016. S6: application and treatment of clays and other industrial minerals.Cost Action Molim, Molecules in Motions, CM 1405; University Paris-Est Marne-La-Vallee, France, 27-29 August 2015This chapter provides an overview of the main biochemical transformations of major elements, including carbon, nitrogen, sulfur, iron and phosphorus in anaerobic digesters. Mineralization of organic matter during anaerobic digestion processes results in the production of inorganic carbonate, ammonium, sulfide, and phosphate species, which are involved in a complex network of chemical and biological reactions through interaction with available macro and micro nutrients as well as microbial processes with profound effects on the efficiency and stability of the anaerobic digester performance. The interplay of iron, phosphorus and sulfur cycles has recently attracted attention in the frame of research developed for the recovery of phosphorus on one hand and in the frame of the