High Temperature Superconductors Components Research Articles

Intrinsic Influence of Dynamic Resistance on Current Distribution of Two HTS Parallel Branches Without Terminal Contact Resistance

If a superconductor carries DC transport current and exposes to an alternating current (AC) magnetic field whose amplitude is more than its threshold field, a DC resistance so called dynamic resistance occurs on the superconductor because of the dissipative interaction between the DC transport current and the external magnetic field, which possibly appears in many kinds of high temperature superconductor (HTS) apparatus, such as linear synchronous motors. Occurrence of the dynamic resistance significantly affects the current distribution of the HTS components connected in parallel such as cables and conductors except for increasing the AC loses. In this paper, we employ a partially slit second-generation (2G) HTS tape with two branches to study the influence of dynamic resistance on current distribution such that the terminal contact resistances can be avoided. In experiment, DC transport current is applied to the whole 2G HTS tape and branch 1# is only exposed to an applied AC magnetic field. In addition, we use an analytical formulation of the dynamic resistance of branch 1# based on Bean critical state model and voltage calculation of branch 2# relies on E-I curve to build analytical model by using Newton Iteration. It is shown that DC current value of branch 1# decreases and branch 2# increases with the increasing of the dynamic resistance of branch 1#. The results are important for HTS DC devices with carrying ripple current or exposed to AC magnetic field.

Transient Test and AC Loss Study of a Cryogenic Propulsion Unit for All Electric Aircraft

This paper reports a pioneering demonstration platform of a cryogenic propulsion unit at liquid nitrogen temperature. A high temperature superconducting (HTS) machine is connected with a cryogenic power rectifier in a generator mode to prove the feasibility of a cryogenic propulsion unit for electric aircraft propulsion applications. Machine operation was carried out with a special focus on the total heat dissipation inside the HTS AC windings. Different types of 2G HTS tapes were tested to provided data for stator coils’ design. The transient operation was carried out to represent a short-circuit failure in one of the power electronic devices. The test shows AC loss performance of the HTS windings using calorimetric method during the short circuit event, indicating the importance of developing protection schemes for the cryogenic propulsion units to prevent damage to the HTS components. The paper provides initial insights into the interaction between superconducting machines and cryogenic power electronics within a cryogenic propulsion unit. It is an important first step to understand and further develop cryogenic propulsion technology for future electric aircraft.

Investigation of HTS cable impact on turbo‐electric aircraft performance

With significant interest in the use of high-temperature superconducting (HTS) components in electric aircraft, there is a need for novel modelling techniques that allow architecture-level studies of the electrical systems including HTS components. In this study, a simple electric network architecture, as proposed in the literature has been considered, which includes generators, dynamic propulsion load and cables. This electric network has been modelled considering conventional technology and using HTS cables by replacing the conventional copper cables, to evaluate the variations in the network performance. The network performance has been studied for the dynamically varying propulsion load, which is nearly equivalent to the aircraft load over the entire flight duration. Following this, electric faults have been applied at various locations, and the impact of HTS cables on the network fault levels has been evaluated. The fault current levels are compared using both conventional and HTS cables, due to the fault current limiting properties of the HTS cables, they are observed to offer lowered fault current values.

AC HTS Transmission Cable for Integration into the Future EHV Grid of the Netherlands

Due to increasing power demand, the electricity grid of the Netherlands is changing. The future grid must be capable to transmit all the connected power. Power generation will be more decentralized like for instance wind parks connected to the grid. Furthermore, future large scale production units are expected to be installed near coastal regions. This creates some potential grid issues, such as: large power amounts to be transmitted to consumers from west to east and grid stability. High temperature superconductors (HTS) can help solving these grid problems. Advantages to integrate HTS components at Extra High Voltage (EHV) and High Voltage (HV) levels are numerous: more power with less losses and less emissions, intrinsic fault current limiting capability, better control of power flow, reduced footprint, etc. Today's main obstacle is the relatively high price of HTS. Nevertheless, as the price goes down, initial market penetration for several HTS components is expected by year 2015 (e.g.: cables, fault current limiters). In this paper we present a design of intrinsically compensated EHV HTS cable for future grid integration. Discussed are the parameters of such cable providing an optimal power transmission in the future network.

Integration of HTS Cables in the Future Grid of the Netherlands

ue to increasing power demand, the electricity grid of the Netherlands is changing. The future transmission grid will obtain electrical power generated by decentralized renewable sources, together with large scale generation units located at the coastal region. In this way electrical power has to be distributed and transmitted over longer distances from generation to end user. Potential grid issues like: amount of distributed power, grid stability and electrical loss dissipation merit particular attention. High temperature superconductors (HTS) can play an important role in solving these grid problems. Advantages to integrate HTS components at transmission voltages are numerous: more transmittable power together with less emissions, intrinsic fault current limiting capability, lower ac loss, better control of power flow, reduced footprint, less magnetic field emissions, etc. The main obstacle at present is the relatively high price of HTS conductor. However as the price goes down, initial market penetration of several HTS components (e.g.: cables, fault current limiters) is expected by year 2015. In the full paper we present selected ways to integrate EHV AC HTS cables depending on a particular future grid scenario in the Netherlands.

Rated-voltage enhancement by fast-breaking of the fault current for a resistive superconducting fault current limiter component

Performance of a resistive superconducting fault current limiter (SFCL) component is usually limited by temperature rise associated with energy input by fault current application during a fault. Therefore, it is expected that short application of the fault current may enhance the power ratings of the component. This can be accomplished by a combination of a HTS component and a mechanical switch. The fast switch (FS) developed recently enables the fault duration to be as short as 1/2 cycle after a fault. Various second-generation (2G) high temperature superconductors (HTS) and YBCO thin films have been tested. The relation between the rated voltage V and the fault duration time t was found to be V2∼t−1. Based upon the relation, we predict that when the FS break the fault current within 1/2 cycle after a fault, the amount of HTS components required to build an SFCL can be reduced by as much as about 60%, of that when breaking the fault current at three cycles.

Use of high-temperature superconducting components in third-generation cellular phone basestations

Use of high-temperature superconducting components in third-generation cellular phone basestations

Fault current limiter based on high temperature superconductors – different concepts, test results, simulations, applications

All electric equipment in a power system has to be designed to withstand the mechanical and thermal stresses of potential short-circuit currents. Any reduction of these currents can lead to significant cost savings. Among all current limiting devices, superconducting fault current limiters (SCFCL) offer ideal performance: in normal operation the SCFCL is in its superconducting state and has negligible impedance, in the event of a fault, the transition into the normal conducting state passively limits the current. Different high temperature superconductors (HTS) materials, like YBCO films, Bi2223 wires or Bi2212 bulk are under development for the use in SCFCL. Due to the brittle nature of HTS and the hot-spot problem, most HTS components for current limitation are composites comprising the HTS, a mechanical substrate or support, and an electrical bypass. The performance of the composites largely depend on the parameters: critical current density, I– V characteristics, thermal conductivity, thermal mass, and electrical bypass. Mainly two different concepts of SCFCL, namely, the “resistive” and the “shielded core” concept have been pursued in the past. In 1996 the first ever SCFCL was installed in a hydro-power plant. The device had a rated power of 1.2 MVA, it was of the “shielded core” type and was based on tubes of Bi2212-bulk material. The feasibility of the technology has been demonstrated in a one-year-endurance test. Recently more compact “resistive” SCFCLs based on the same Bi2212-bulk material have been developed. Theoretical models for the SCFCL show good agreement with experimental data. They are used to study the influence of SCFCLs in power systems in order to evaluate technical and economical advantages.

Magnetism and Superconductivity

Australian Superconductors has introduced an improved range of high-temperature superconductor (HTS) tapes designed for use in electrical machinery operating at 77 K. The tapes are made using powder-in-tube techniques to incorporate ceramic filaments of bismuth-2223 into a matrix of silver or silver alloy. The design can be adapted to meet customer requirements by using different sheathing materials or by altering the number of filaments to optimize the thermal loss and mechanical strength of the tape. The superconducting filaments can also be twisted for low AC loss, or supplied in tape-in-tube, wire-in-tube or parallel stack formats. Fully constructed components and artefacts made using the tape are available in coiled-in-racetrack, solenoidal or torroidal formats, or stranded and braided in high- current busbars, leads and cables. The company also offers analytical services, standards and design of HTS components and devices.

Superconducting AC/DC power coversion using high-temperature superconducting components

The trend towards DC transmission of power, especially when using superconductors, has made the conversion of power from AC to DC and DC to AC a critical element of many electrical systems. We designed and tested an AC to DC and DC to AC converter which used HTS cryotron switches. The superconducting elements were made from yttrium barium copper oxide, and the converter was operated at 77 Kelvin. Both AC to DC and DC to AC conversion has been demonstrated, and the conversion has been shown to be relatively independent of frequency over a wide range. The converter was tested with a current of a few amperes, but is upwardly scalable to thousands of amperes, At larger currents the converter is more efficient as much of the power loss occurs in a separate control circuit which carries a current that does not scale with the amount of current controlled. Significant sources of inefficiencies remain which make the initial device impractical for actual use; however, the proposed improvements in material and design should allow the converter to be used in practical applications and outperform conventional methods of conversion such as thyristors.

The High Temperature Superconductivity Space Experiment: Present Status and Future Challenges

ABSTRACT The High Temperature Superconductivity Space Experiment (HTSSE) at the Naval Research Laboratory (NRL) is exploring the feasibility of deploying high temperature superconducting (HTS) electronic devices, components and subsystems in space. The initial HTSSE experiment, which employed HTS technology available in 1990, focused on simple microwave devices which were suitably packaged, integrated with a cryogenic refrigerator and built into a space‐qualified payload. Unfortunately the HTSSE‐I payload, which was to have been launched in 1993, did not achieve orbit and was lost. The second HTSSE experiment, HTSSETI, which employs HTS technology circa 1993‐94, consists of complex HTS components and hybrid subsystems consisting of HTS and conventional semiconductor components, the latter operating either at cryogenic temperature or at room temperature. The HTSSE‐II payload containing the HTS components, cryogenic refrigerator and monitoring electronics was built, space qualified and shipped from NRL to the satellite integrator in the Spring of 1996. The launch of HTSSE‐II on the Advanced Global and Research Observation Satellite (ARGOS), which was originally set for mid‐1996, is now scheduled for March 1998. A description of the HTSSE‐II payload will be presented and the performance of the HTS components and their potential impact on future space communications systems will be described.

High-temperature superconducting beam forming network for communication system applications

This paper presents an application of the high-temperature superconductor (HTS) technology to the development of a high-performance antenna beam forming network (BFN) for communication systems. Design and measurements are made in Ku-band with a multiple power divider technique involving a cascade of 3-dB branch-line couplers. Three microstrip couplers are integrated to form a one-to-four BFN. An experimental prototype is fabricated with TlBaCaCuO thin film deposited onto LaAlO/sub 3/ substrate. Power handling capability of related HTS components such as line, bend, and BFN are also studied together with third-order intermodulation characteristics. It is shown that theoretical prediction is consistent with experimental results, presenting insertion loss of the four output ports ranging from 6.1-6.4 dB and return loss better than 14 dB at 11.95 GHz. These preliminary results demonstrate the potential of extending such a power divider technique in designing an N-port BFN. It is also indicated that the proposed HTS BFN scheme can offer advantages compared to its conventional counterpart, namely, a significant reduction in size/weight and low power loss.

Jet Propulsion Laboratory/NASA Lewis Research Center space qualified hybrid high temperature superconducting/semiconducting 7.4 GHz low-noise downconverter for NRL HTSSE-II program

A deep space satellite downconverter receiver was proposed by Jet Propulsion Laboratory (JPL) and NASA Lewis Research Center (LeRC) for the Naval Research Laboratory's (NRL) high temperature superconductivity space experiment, phase-II (HTSSE-II) program. Space qualified low-noise cryogenic downconverter receivers utilizing thin-film high temperature superconducting (HTS) passive circuitry and semiconductor active devices were developed and delivered to NRL. The downconverter consists of an HTS preselect filter, a cryogenic low-noise amplifier; a cryogenic mixer, and a cryogenic oscillator with an HTS resonator. HTS components were inserted as the front-end filter and the local oscillator resonator for their superior 77 K performance over the conventional components. The semiconducting low noise amplifier also benefited from cooling to 77 K. The mixer was designed specifically for cryogenic applications and provided low conversion loss and low power consumption. In addition to an engineering model, two space qualified units (qualification, flight) were built and delivered to NRL. Manufacturing ,integration and test of the space qualified downconverters adhered to the requirements of JPL class-D space instruments and partially to MIL-STD-883D specifications. The qualification unit has /spl sim/50 K system noise temperature which is a factor of three better than a conventional downconverter at room temperature. Commercial applications such as intersatellite links and V-SATS are envisioned to benefit by >3 dB link margin, or a factor of 2 in antenna size, from a future hybrid HTS/semiconducting cryogenic receiver employing new InP based HEMT LNA. In a spread spectrum communication network, the number of users per beam would more than double.

A space-qualified experiment integrating HTS digital circuits and small cryocoolers

High temperature superconductors (HTS) promise to achieve electrical performance superior to that of conventional electronics. For application in space systems, HTS systems must simultaneously achieve lower power, weight, and volume than conventional electronics, and meet stringent space qualification and reliability requirements. Most effort to date has focused on passive RF/microwave applications. However, incorporation of active microwave components such as amplifiers, mixers, and phase shifters, and on-board high data rate digital signal processing is limited by the power and weight of their spacecraft electronic and support modules. Absence of data on active HTS components will prevent their utilization in space. To validate the feasibility in space of HTS circuits and components based on Josephson junctions, we need to demonstrate HTS circuits and critical supporting technologies, such as space-qualified packaging and interconnects, closed-cycle cryocooling, and interface electronics. This paper describes the packaging, performance, and space test plan of an integrated, space-qualified experimental package consisting of HTS Josephson junction circuits and all the supporting components for NRL's high temperature superconductor space experiment (HTSSE-II). Most of the technical challenges and approaches are equally applicable to passive and active RF/microwave and digital electronic components, and this experiment will provide valuable validation data.

The high-temperature superconductivity space experiment (HTSSE): present status and future challenges

The high-temperature superconductivity space experiment (HTSSE) at the Naval Research Laboratory (NRL) is exploring the feasibility of deploying high-temperature superconducting (HTS) electronic devices, components and subsystems in space. The initial HTSSE experiment, which employed HTS technology available in 1990, focused on simple microwave devices which were suitably packaged, integrated with a cryogenic refrigerator and built into a space-qualified payload. Unfortunately the HTSSE-1 payload, which was launched in 1993, did not achieve orbit and was lost. The second HTSSE experiment, HTSSE-II, which will use HTS technology circa 1993 - 94, will consist of complex HTS components and hybrid subsystems consisting of HTS and conventional semiconductor components, the latter operating either at cryogenic temperature or at ambient temperature. The HTSSE-II payload containing the HTS components, cryogenic refrigerator and monitoring electronics will have been built, space qualified and shipped from NRL in November 1995 to the satellite integrator for a planned Summer 1996 launch. A description of the HTSSE-II payload will be presented and the performance of the HTS components and their potential impact on future space communications systems will be described.

Weight and power considerations for the design of a cryogenically cooled HTS electronic system

Abstract Much progress has been reported on the fabrication of high temperature superconducting (HTS) electronic devices, circuits and systems. In some of these reports, comparisons have been made between the electrical behavior of HTS components and their “equivalent” semiconductor counterparts. Unfortunately, in almost all cases, the comparisons have been made at the device or circuit level. In an operational system, the HTS chip(s) must be mounted in an efficiently insulated cryogenic enclosure and integrated with a closed cycle cryogenic refrigerator (“cryocooler”) or an open-cycle dewar system. Therefore, to perform a meaningful comparison of an HTS system with a conventional (ambient temperature) one, the HTS system must include, in addition to the electronic chips, the cryogenic enclosure and cryogenic refrigeration system. In addition, the weight, volume, electrical input power and cool-down time for the cryogenic subsystem must also be taken into account in making such a comparison. That is, meaningful performance comparisons must be made at the system level.

SNMS studies of high temperature superconductor films on silicon

The reproducible deposition of high temperature superconductors (HTC) on Silicon substrate is of central importance for taking full advantage of HTC passive interconnects between VLSI circuits. Up to now the main obstacle are the dramatic mismatch between processing temperature of HTC and the temperature allowed in standard VLSI silicon technology. Suppression of interdiffusion of HTC components and the Silicon substrate is one of the most challenging tasks. In situ deposition of HTC on bare silicon substrates leads to strong interdiffusion, deteriorating the superconducting properties of HTC. To solve this problem diffusion blocking barriers are investigated. We have checked the feasibility of Si 3N 4 and SiO 2 as barrier for the material-systems YBaCuO and BiSrCaCuO. Electrongas SNMS has been applied for chemical analysis of depth distribution of the different elemental species. Electrongas SNMS supplies high depth resolution and excellent sensitivity.