Search

Flux pumps provide a contact-free method of energizing dc currents in superconducting coils. Since a predictive quantitative theory for dynamo-type flux pumps does not exist yet, the optimization of device designs must proceed through empirical experiment. In this paper, we investigate the effect of varying the annularwidth of the iron stator yokewithin a high-temperature superconducting dynamo. Reducing the dimensions of this iron yoke reduces the mass of cold iron within the dynamo, and hence has advantages in terms of weight, cryogenic efficiency, and eddy current losses. In this paper, we have investigated the dc output from an experimental high-temperature superconductor (HTS) dynamo in which the annular width of the iron yoke Δr is varied across a factor of four. Varying this dimension affects the reluctance of the magnetic circuit formed between the rotor and stator. We have shown that the dynamo output is surprisingly insensitive to the size of the iron yoke. The maximum current output (Isc ) is independent of Δr at all flux gaps. At the closest magnet-stator flux gap, a fourfold increase in Δr results in only a ~30% increase in the open circuit voltage (Voc ) and internal resistance (Rd) of the dynamo. Our results indicate that the smallest yoke studied (Δr = 6 mm) can be utilized with a 25.4-mm Nd-Fe-B rotor magnet, without adverse impact on the electrical performance of this type of HTS dynamo. [ABSTRACT FROM AUTHOR]

This paper presents the design and experimental results of a coreless superconducting fault current limiter (SFCL). The limiter has a rating of 15 kV and 140 A and was tested with a 2.5 GVA short-circuit generator. During the occurrence of a short circuit, the elements of the system are less exposed to electrodynamic and thermal overloads. The application of an SFCL leads to an increase of the capability of the power network for connecting distributed generation energy sources. Compact design of the coreless superconducting fault current limiter consists of three magnetically coupled windings cooled in liquid nitrogen. A high magnetic coupling between the superconducting windings gives a very low voltage on the limiter at a nominal current. The presented solution reduces size and weight of the device. The paper summarizes the design of the coreless limiter and presents in detail the results of tests performed at a high-power test facility. [ABSTRACT FROM PUBLISHER]

A higher magnetic field can provide more opportunities to reveal new phenomena in a scientific research. Aiming to achieve a higher magnetic field, Wuhan National High Magnetic Field Center (WHMFC), Wuhan, China has designed a a power supply system for 100 T magnetic field under existing power supply conditions in April 2015. The 100 T magnet consisting of three coils is energized by a multipower supply system. The outer coil is energized by a pulsed generator-rectifier connected to battery bank in series. The middle coil and the inner coil are energized by two capacitor bank, respectively. To ensure safety and reliable operation, control sequence as well as protection system for the power system is designed and developed. A test system including the prototype of three-coil magnet is established at WHMFC. A series of tests are carried out on hybrid power supply systems. 73.3 T peak field has been achieved as the highest magnetic field in the test. The test results presented in this paper show the hybrid power supply system is feasible and operable. [ABSTRACT FROM AUTHOR]

In the framework of the development of high field magnets made of Nb3Sn superconductors for projects like the high luminosity upgrade of the large hadron collider (HL-LHC) and FCC studies, it is necessary to refine the understanding of the winding process and its impact of the overall mechanical integrity of the conductor. The mechanical behavior during winding of the unreacted Rutherford-type Nb3Sn cables has been studied experimentally. In order to quantify the windability of the various cable designs, the measurementmethod and a dedicated specimenscanning device has been developed. The validation of the device and achieved repeatability are presented in this paper. The results from the first winding test campaign with cables 11 T dipole RRP, 11 T dipole dummy Cu, MQXF, FRESCA 2, and NbTi are shown. [ABSTRACT FROM AUTHOR]

In this paper, the transformer-type superconducting fault current limiter (SFCL) with additional circuit, which could limit the fault current through twice quench operations, was suggested. The suggested SFCL includes one primary winding, two nonisolated secondary windings wound on the same iron core, and two high-TC superconducting elements connected with each secondary winding. The advantage of the suggested SFCL is that it can perform the twice current limiting operations due to the transient amplitude of the fault current. Among its design parameters, the winding direction of another secondary winding comprising the additional circuit of the transformer-type SFCL or the nonisolated secondary winding is expected to affect its fault current limiting characteristics. To analyze the dependence of the fault current limiting operation on the winding direction of two nonisolated secondary windings, two limiting operational currents from its electrical equivalent circuit were derived. Through the fault current limiting tests for the suggested SFCL, the fault current limiting characteristics of the SFCL were discussed. [ABSTRACT FROM AUTHOR]

This paper presents the characteristics analysis of the flux-switching synchronous generator (FSG) applying noinsulation (NI)-type high-temperature superconducting (HTS) field coils. The HTS FSG can be cost effective, since the field coils and armature windings are both installed in the stator, while the rotor is onlymade of iron corewith tooth. Alongwith lowcost, since HTS field coils in the FSGs are located in the stationary part of the generator, FSG can be a solution for the design complexities of the excitation and cooling systems for HTS field coils. In addition, several studies on HTS coils without turn-to-turn insulation (NI) have been reported for HTS field coils for applying in electrical rotating machines. The NI-type winding technique enhances the stability of the HTS field coil since the overcurrent is automatically bypassed through the contacts between winding turns. Nevertheless, there is still an issue about whether the NI-type HTS field coil can be applied to the electrical rotating machines. In this study, we fabricated and tested an NI-type HTS field coil. In addition, a 600-kW HTS FSG was designed using a fundamental design process and the characteristics analysis of the generator was performed based on the test results of the fabricated NI-type field coil. The results show that the HTS FSG having NI-type HTS field coils is able to operate normally under normal operating conditions. However, the field current charging problem issue has been revealed through this study. Therefore, further research will need to improve the problem. [ABSTRACT FROM AUTHOR]

The SUPRAPOWER, an EU FP7 funded research project, is developing an innovative 10 MW class superconducting generator to provide an important breakthrough in the offshore wind industry. The 10 MW generators adopts modular concept to the superconducting coil and associated cryogenic systems. And the modular superconducting coil and cryostat of this novel generator will be validated through a scale-down rotating magnetic validator (RMV). The cryogenic cooling system for the RMV consists of two modular cryostats: a distributing cryostat and the corresponding rotating cryocooler system with a self-developed rotary joint. In order to achieve the SC coils' working temperature of 20 K, a two-stage G-M cryocooler will be applied and linked to the two modular cryostats by way of a conductive copper connection. The distributing cryostat was developed to envelop the cold head of the cryocooler, thermal link, and three binary current leads to electrically feed the coils. A rotary joint with Ferrofluid sealing was developed to transfer the helium gas between the rotating cold head and stationary oil-lubricated compressor. In this paper, the design, manufacture, and assembly of this cryogenic system for RMV will be presented in detail. [ABSTRACT FROM AUTHOR]

For the cryogenic system of large capacity superconducting motors, a rotary joint (RJ) is usually installed to translate the fluid coolant from the static reservoir to the rotary cryostat in the superconducting motor. However, the sealing performance and heat generation and heat load are still not solved, essentially. In this paper, based on the characteristics of the large capacity wind generator with low revolution speed and sufficiently large space in the rotor, a novel cryogenic system suitable for 10 MW superconducting wind generators is proposed, with which the RJ can be removed. The design process of the cryogenic system is illustrated in detail. The characteristic analysis of the proposed cryogenic system is compared with the topology with the RJ from the aspects of sealing performance, heat generation and heat load, and the transmission line. It can be found that the proposed cryogenic system can improve the cooling efficiency and reduce the cooling cost. [ABSTRACT FROM AUTHOR]

Wave energy converters (WECs) have received much attention with the increasing environmental concerns. And the direct-drive WECs are more attractive due to the elimination of intermediate mechanical conversion parts. We have proposed a concept of a WEC device, in which a tubular linear generator (TLG) is directly driven by a heaving buoy. We design a high-temperature superconducting TLG (HTS-TLG), a permanent magnet (PM) TLG, and a copper TLG for the WEC. In this paper, we give a brief description on the conceptual structures and the electrical design method of these three types of TLGs, then show the way of determining main machine parameters considering the basic generator performance (weight, efficiency, and the amount of field conductors/PMs). Design results of these TLGs are finally presented with machine performances and costs compared. We found that the HTS-TLG is the most promising one compared to the other counterparts. [ABSTRACT FROM PUBLISHER]

In this paper, a new linear Vernier permanent-magnet machine is proposed. By using high-temperature superconducting (HTS) winding to provide an additional field excitation, a hybrid excitation machine is achieved. The HTS field winding is accommodated in the stator and PMs are mounted on the mover surface. By regulating the dc current flowing in the HTS field winding, the air-gap flux can be flexibly controlled. First, the proposed machine and the cooling system for the HTS field winding are presented. Second, the operating principle of the proposed machine is discussed. Third, by using the 3-D finite element method, the performance of the proposed machine is evaluated. Finally, a conclusion is drawn. [ABSTRACT FROM PUBLISHER]

Due to the anisotropy of a tape-shaped HTS wire, the method to determine the operating current of an HTS magnet needs to be different from that of a LTS magnet. This paper presented estimation of the critical current of pancake windings excited by multiple power sources. Critical currents were determined by using field dependent E-J relation. A new method to define the magnetic field of the HTS wire has been proposed in this paper. Calculated critical currents of pancake windings were compared with measured ones of the HTS BSCCO magnet consisting of 10 pancake windings. Effects of multiple power excitation on the increment of the central magnetic field has been also described. Test results showed the estimated critical currents of pancake windings agreed well with that of measured ones and the central magnetic field was increased at multiple power excitation by 28.4% comparing with that of single power excitation. [ABSTRACT FROM AUTHOR]

The thermal stability and quench propagations are one of the most fundamental issues for the High Temperature Superconducting (HTS) coil. Superconductivity is confined within the phase surface bounded by magnetic field, temperature, and current. Of these three parameters, the temperature is neither completely controllable, nor predictable, because the energy stored in the magnet, can easily be converted into heat up setting the thermal equilibrium within the winding. Therefore, in HTS coil operation, the temperature stability or more generally the thermal behavior of the conductor is the most important. In this paper, a HTS double racetrack pancake coil was prepared to examine the thermal stability, quench propagation and minimum quench energy (MQE). HTS coil was wound using the AMSC Bi-2223. The experimental results are discussed in this paper. [ABSTRACT FROM AUTHOR]

In 1966, following a decade of discovery and development on A15 compounds, Richard Garwin and Juri Matisoo [1], two research staff members then in the IBM Research Division, submitted for publication a paper examining the prospect to employ one of the most promising of these materials, Nb3Sn, in a cable system for transmission of electricity. The scale of their proposal was truly enormous -100 GW (+/-100 kV at 500 kA direct current) over a distance of 1000 km, the entire length refrigerated by liquid helium. At the time, such a cable would have been capable of carrying half the entire electric power generated in the United States, and about one-tenth today. This paper will revisit their vision in the context of the subsequent discovery of high temperature superconductivity twenty years later, and the now emerging availability of long lengths of high performance wire and tape for operation in the 20–80 K range. Whereas the scenario set by Garwin and Matisoo addressed the one-way transmission of electricity from remote coal and nuclear generation multi-plant ‘farms’ to large population centers, we will extend their picture to include two-way transmission on a diurnal or longer period to take advantage of regional electricity pricing and production which has resulted from the deregulation of generation. We conclude that the advent of high temperature superconductivity substantially extends and brings closer both the technical and economic feasibility of Garwin and Matisoo's dream. However, we note, as did they, the caveat that ‘whether it is desirable or necessary is another matter entirely.’ We believe this question will be decided in the affirmative as societal demands continue to increase for the clean, reliable and ecologically gentle delivery of large amounts of electric power, a need that was foreseen but not as overriding forty years ago as it is now. [ABSTRACT FROM AUTHOR]

A high temperature superconducting (HTS) motor has been designed to power a general aviation aircraft. The propulsion requirements of the Cessna 172 have been chosen as baseline for the study: 200 HP at 2700 RPM. The designed motor is based on flux trapping in bulk YBCO plates and concentration of the flux generated by Bi-2223 coils and an ironless air-cooled resistive armature. The eight-pole machine would exhibit high power density comparable to that of small gas turbines around 4 HP/lb. Details of this HTS motor concept have been presented in a previous paper. However, the scaling up of such a configuration is not straightforward, as single domain YBCO elements cannot exceed a few centimeters in diameter. This paper presents the design of a motor based on the same configuration but with a much higher power rating, in the range of several MW, to power High Altitude Long Endurance (HALE) aircraft or small jets. Due to the size limitation of the YBCO plates, two solutions can be used to increase the power: the radius and the number of poles can be increased, or the motor can be lengthened to accommodate more coil-plate pairs. The motor is able to reach more than 2 T in the air gap thus leading to high power density. The design optimization is done with respect to several objectives as a trade-off between amount of superconductor, efficiency, weight and volume. The cooling system is assumed to be provided by liquid hydrogen available onboard the aircraft as fuel for the fuel cells or turbo-generators. [ABSTRACT FROM AUTHOR]

A no-insulation winding technique for an NbTi superconducting coil is expected to improve its dynamic stability during charging or discharging. Experimental results, recently reported, demonstrated the charging stability enhancement of an NI coil. In an NI winding, an amount of current can bypass to adjacent wires to avoid the generation of a local hot spot and, as a result, the dynamic stability is improved. In spite of the potential technical merits of the NI technique, the charging responses of an NI coil, including the non-uniform current distribution under a time-varying condition, have not been investigated analytically yet. In this paper, we propose a simulation method using an equivalent circuit equation for an NI coil with its inductance and the contact turn-to-turn resistances taken into consideration. The simulation results were analyzed in three aspects: terminal voltage, loss energy, and stored magnetic energy. [ABSTRACT FROM PUBLISHER]

This paper presents a new electromagnetic vibration-powered generator. In the generator, the moving mass has a sandwich structure, consisting of two axially magnetized annular permanent magnets and one soft magnetic “pole piece.” The purpose of using the soft magnetic pole is to increase the effective flux linkage of the generator and to increase the output voltage of the generator. The generator makes use of a “magnetic spring,” which gives advantages such as ease of construction, ease of tenability, and less prone to fatigue as opposed to a mechanical spring. The mathematical model of the generator was built. The magnetic field distribution of the designed generator was analyzed by means of finite-element method. The prototype generator was built and tested with a force control electromagnetic shaker. Tests results of output waveforms have shown good agreement with simulation results. The open circuit RMS voltage of the presented generator is 662.0 mV, which increases by an additional 13.5% the one of conventional structure, at a resonance frequency of 15 Hz and an amplitude of 3 mm. [ABSTRACT FROM PUBLISHER]

This paper presents a new hybrid piezoelectric-electromagnetic vibration-powered generator (HPVG). An electromagnetic generator and a piezoelectric generator are combined as an integrated HPVG. An input-output mathematical model describing the coupling of the mechanical filed, electrical field, and magnetic field in the HPVG is presented. The resonant frequency, the output voltage waveforms, and the output power have been studied. The HPVG has a much higher power output compared with a single piezoelectric generator or an electromagnetic generator of the same dimension. [ABSTRACT FROM PUBLISHER]

Superconducting Fault Current Limiters (SFCLs) are expected to be installed in the power system for improving their reliability and stability. The three-phase transformer type coaxial SFCL with rewound structure have been proposed and designed in the past. Due to the rewound structure, internal magnetic field of an SFCL is cancelled and each phase of the SFCL can work independently without interference with the other coaxial phases. This paper describes current limiting performance and recovery characteristics in Recovery Under Load (RUL) operation of the proposed SFCL. The operation tests of the SFCL under load were carried out on a lab-scale model power system (one generator, double-circuit transmission line, and infinite bus system). In this system, faults occurred on one line. The SFCL was installed in the generator terminal in series and the generator continued to supply power to another line through the SFCL in fault sequence so the SFCL operated in RUL. It was confirmed that the SFCL limited the fault current from approximately 600 to 250 A, reduced the burden of the generator, and successfully recovered to superconducting state. [ABSTRACT FROM PUBLISHER]

This paper presents a study on the effects of winding tension on the characteristic resistance of a no-insulation (NI) coil. Two ReBCO NI test pancake coils, having the same winding i.d. (60 mm), o.d. (67.6 mm), and number of turns (60), were sequentially prepared in a way that the first test coil was wound with a winding tension of 12-N, tested, and then rewound with a new winding tension of 20-N for the same tests. In each test, the test coil was energized at a target current, the power supply was “suddenly” disconnected, and then the temporal decay of the coil center field was measured, from which the time constant of the test coil and the consequent characteristic resistance were obtained. To check the reproducibility of experimental data, each test was repeated four times and each time the test coil was unwound and rewound with a given winding tension. The experimental results were analyzed with equivalent circuit analyses. Correlation between the winding tension and the characteristic resistance was discussed in detail. [ABSTRACT FROM PUBLISHER]

The integration of wind turbines into modern power grids has significantly increased during the last decade. Wind turbines equipped with doubly fed induction generators (DFIGs) have been dominating wind power installation worldwide since 2002. In this paper, a superconducting magnetic energy storage (SMES) unit is proposed to improve the dynamic performance of a wind energy conversion system equipped with DFIG during voltage sag and voltage swell events. The converter and the chopper of the SMES unit are controlled using a hysteresis current controller and a fuzzy logic controller, respectively. Detailed simulation is carried out using MATLAB/SIMULINK software to highlight the impact of the SMES unit in improving the overall system performance under voltage sag and voltage swell conditions. [ABSTRACT FROM PUBLISHER]

In a High Temperature Superconducting (HTS) magnet consisting of pancake windings, HTS tape with the same width has been used for all pancake windings. If a wider HTS tape is used for the outer pancake windings, the critical current of the HTS magnet can be increased. This paper shows the properties of BSCCO magnets in which the outer pancake windings are wound with a wider HTS tape. In order to examine the effects of a wider HTS tape, a HTS magnet with an inner radius of 20 mm and a height of 202.4 mm was used. The number of turns of each pancake winding was 150, and the number of pancake windings was 46. The critical current of the pancake winding was determined by using E-J relation. Results of calculation show that the critical current was higher in the HTS magnet with a wider HTS tape at the outer pancake windings than in the HTS magnet with the same width of HTS tape for all pancake windings. [ABSTRACT FROM PUBLISHER]

This paper presents a new electromagnetic vibration-powered generator. The input-output mathematical model of an axial magnetization annular permanent magnet spring is built. Taking advantage of the model, the characteristic curve of the magnetic force versus the displacement is obtained. Wires were wound both inside and outside of the annular permanent magnet to form an inner coil and an outer coil, respectively. The characteristic curve of the magnetic force, the natural frequency, the output voltage waveforms of the outer coil and the inner coil, and the magnetic field distribution of the designed generator have been simulated using the Finite Element method (FEM). Tests results of the output waveforms have good agreement with the simulation results. The maximum output power of the designed vibration-powered generator is 28.3 mW, and the open circuit RMS voltage is 5.1 V at an vibration frequency of 20 Hz and an amplitude of 5 mm. [ABSTRACT FROM PUBLISHER]

In the High Magnetic Field Laboratory, Chinese Academy of Sciences, a model coil has been fabricated and tested with the intention of developing the manufacturing technique and confirming the research and development routine of the superconducting outsert for a 40-T hybrid magnet. The model coil was layer wound using a \Nb3\Sn cable-in-conduit conductor with small radius due to the restriction of the inner diameter of a NbTi solenoid coil, which will provide a central 7.5-T background magnetic field for the model coil tests. In normal operation, the highest field on the model coil conductor would reach about 12 T. The manufacturing process of the model coil included conductor forming, winding, heat treatment, vacuum impregnation, and assembly. For the purpose of summarizing the whole manufacturing process, in this paper, the important fabrication techniques are introduced and discussed. [ABSTRACT FROM AUTHOR]

Various energy storage systems have been adopted in power systems for economic and reliability reasons. In order to maintain the reliability of power systems, reserve power needs to be scheduled against possible generation unit outages. The variation of wind power outputs also requires additional reserve power in addition to the reserve for the possible generation unit outages. Superconducting Magnetic Energy Storage (SMES) has a potential for providing regulation power to meet the reserve requirements in power systems involving wind power generators. This paper presents a stochastic method for the optimal operation of a power system with wind generators and SMES systems. Numerical simulation results are presented to illustrate the potential application of SMES systems to power systems. [ABSTRACT FROM AUTHOR]

This paper analyses the effect of a superconducting fault current limiter (SFCL) on the optimal sizing of a wind-turbine generator system (WTGS), which is a representative renewable energy source. When the WTGS is connected to a radial distribution system, the level of fault current during a contingency is increased. This increased fault current can reduce the coordination time intervals (CTIs) between multiple overcurrent relays, which are an important factor in determining the optimal size of the WTGS. Moreover, the maximum capacity of WTGS is also restricted by the associated fault current level and CTIs in a power system. [ABSTRACT FROM AUTHOR]

The vibration energy exists widely and is always wasted. Energy harvesting devices that convert kinetic energy into electrical energy have attracted much interest. A variety of vibration driven generators using electromagnetic principles to convert the kinetic energy into electrical energy, are being studied for powering sensors. However, the power supply is always a bottleneck problem to the development of handheld electronic equipments and some other low power electrical apparatus. In this paper, the vibration-to-electrical power generator has been designed and its magnetic field distribution has been analyzed by using Finite Element method (FEM). Then, the input-output model of the generator is built on the basis of vibration equation and law of electromagnetic induction. The calculation result has shown that output voltage of the generator depends on the amplitude, frequency and waveform of a vibration source. A generator prototype has been fabricated and tested at open-circuit and different loads, such as resistances, inductances and capacitances. The comparison of experimental result with calculating one has shown that the model can describe the input-output relation of the vibration-to-electrical power generator. [ABSTRACT FROM AUTHOR]

A novel energy storage system based on a SMES cooled by cryogenic fuel is being developed at the Dept. of Electrical Engineering of the University of Bologna. The system represents an alternative solution with respect to nowadays battery packs for the storage of electrical energy with large specific power. The device may find suitable application on board of road vehicles fed by liquid hydrogen with hybrid power-train (internal combustion engine and electric motor/generation), where a cryogenic tank is already present and no additional cryogenic costs are needed. The housing of the SMES inside the tank used for fuel storage, allows the exploitation of the thermal power required for the continuous evaporation of fuel for feeding the engine to remove the AC losses from the magnet, thus avoiding the need of externally supplied cooling power. In this paper both the design of the magnet and its operation in combination with electronic converter and electric motor/generator during charge/discharge cycles are discussed. Moreover the ongoing activity for the development of a laboratory-scale prototype using MgB2 superconductor is presented. [ABSTRACT FROM AUTHOR]

General Electric, under contract with the Air Force Research Labs (AFRL), has successfully developed and tested a high speed, multimegawatt superconducting generator. The generator was built to demonstrate high temperature superconducting (HTS) generator technology for application in a high power density Multimegawatt Electric Power System (MEPS) for the Air Force. The demonstration tested the generator under load conditions up to 1.3 MW at over 10,000 rpm. The new MEPS generator achieved 97% efficiency including cryocooler losses. All test results indicate that the generator has a significant margin over the test points and that its performance is consistent with program specifications. This demonstration is the first successful full-load test of a superconducting generator for the Air Force. In this paper we describe the development of the generator and present some key test results used to validate the design. Extrapolation to a higher power density generator is also discussed. [ABSTRACT FROM AUTHOR]

In the HTS magnet consisting of pancake windings, all pancake windings have been connected in series and excited by a single power source. Most of the pancake windings cannot conduct their critical current values at single power excitation. Current of each winding can be controlled separately to its critical current at multiple power excitation. This paper presents the excitation of an HTS YBCO magnet consisting of pancake windings by multiple power sources. To estimate the critical currents of the pancake windings more precisely, the magnetic field variation in the HTS wire was considered. Properties of multiple power excitation were measured by using the HTS YBCO magnet consisting of 8 pancake windings. Test results showed calculated currents agreed very well with measured ones and central magnetic field increased by multiple power excitation. [ABSTRACT FROM AUTHOR]

Keystoned superconducting Rutherford cables are widely used in accelerator magnets like in the LHC at CERN. An essential requirement in the cable design is its stability against local heat releases in the magnet windings originating from for example, strand movement or beam loss. Beam loss is the highest at the coil inner radius of the magnet, where also the magnetic field peaks. Also the local compaction of the cable is maximum here and hence the helium content minimum. When performing stability measurements on several superconducting Nb-Ti cables used in LHC dipole and quadrupole magnets, we observed that the stability against point-like heat disturbances is much worse very close to the cable edges as compared to the central part of the cable. The main reason is related to the geometry of the cable causing variation of many parameters across the cable width, like inter-strand electrical resistance, inter-strand heat conductivity, cooled strand surfaces and RRR. In this paper we show results of new stability experiments and thoroughly compare the data with results obtained with the numerical network model CUD!, which is updated for stability simulations. [ABSTRACT FROM AUTHOR]

In order to investigate the quench behavior of conduction cooled MgB2 magnets, a 100 mm inner bore diameter, 0.84 T at 20 K magnet has been built and tested. The test magnet consists of 4 double pancakes wound with the MgB2/Ni-Cu-Fe tape produced by Columbus. Each coil is cooled by means of a 2 mm thick copper disk placed during winding at the middle of the double pancake; after winding the double pancakes have been separately epoxy impregnated. Several experiments have been performed inducing a local transition in the coil by means of a controlled heater placed on the double pancake surface. The propagation of the normal zone has been monitored by means of 8 voltage probes positioned along the tape during coil manufacturing. Each voltage probe detects the voltage drop across a tape length of 30 mm. The experiments have been performed at different temperatures while keeping the magnet current constant during quench. In the paper we report an analysis of the quench propagation velocity measurements and a numerical investigation of the thermal and electrical behavior of the magnet. [ABSTRACT FROM AUTHOR]

In this paper, the design, fabrication and tests of a 1 MJ HTS magnet for SMES was presented. The magnet was fabricated by BSSCO tapes, it consisted of 44 pancakes, the inner diameter of the winding is 400 mm, the outer diameter is 568 mm and the height is 648 mm, the inductance is 6.38 H and the rated operation current is 560 A at 4.2 K. The tests show the magnet could be operated at the design parameters. The magnet will be used for the 1 MJ/500 kVA SMES unit which will be demonstrated at a 10 kV substation in Beijing. [ABSTRACT FROM AUTHOR]

Generally speaking for a HTS coil, perpendicular magnetic field to conductor's broad surface should be suppressed as small as possible in relation to the magnetic anisotropy. This is a reason why toroidal coil with relatively many elementary coils is expected for HTS-SMES. On the other hand, from the point of view of the homogenization of critical current distribution in the coil, perpendicular field and parallel field should be balanced corresponding to the ratio of the magnetic anisotropy. This means that a certain level of the perpendicular field is effective to reduce local heat generation in the coil. Furthermore, this concept is especially reasonable for a high-field coil with usual winding method (flat-wise winding) because the perpendicular field does not induce hoop stress which decreases the critical current. In this paper, we show these findings through an optimal design of a MOCVD-YBCO toroidal coil for 2 GJ class SMES taking account of magnetically and mechanically influenced J - E characteristics. [ABSTRACT FROM AUTHOR]

This paper describes design and operation of a three-phase HTS power transformer with capacity of 630 kVA operated in liquid nitrogen of 77 K for primary/secondary voltages of 10.5 kV/0.4 kV. The windings were wound by hermetic stainless steel-enforced multifilamentary Bi2223/Ag tapes. The structures of primary and secondary windings are solenoid and double-pancake respectively. Cryostat is made from electrical insulating materials with room temperature bore for commercial amorphous alloy core. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests. The ac losses were calculated and measured by method of conventional transformer. The HTS power transformer successfully operated in a live power grid. [ABSTRACT FROM AUTHOR]

When a synchronous generator connected to the power grid experiences a fault, it is required to stay on line, ride through the fault, and be able to carry full rated field current when the fault is cleared. The peak current during these events could be 2 times higher than the normal operating current. This may cause an HTS rotor coil to go into normal state and generate Joule heating. If the fault event is short enough and the heat dumped can be carried away by the cooling system, the coil may recover to the superconducting state at the end of the fault. Otherwise, the coil may thermally run away, or ‘quench’. To investigate the quench behavior of the HTS rotor coil of the 100 MVA generator at GE Global Research Center, a 1.5 MVA prototype coil was developed and tested to quench under different conditions. The experiment design, set up, tests and test results are presented in this paper. [ABSTRACT FROM AUTHOR]

This paper presents design and test of a single-phase HTS transformer with capacity of 45 kVA operated in liquid nitrogen of 77 K for primary/secondary voltages of 2400/160 V. The windings were wound by stainless steel-enforced multifilamentary Bi2223/Ag tapes. The structures of primary and secondary windings are solenoid and double-pancake respectively. The gas-cooling current leads of secondary windings were chosen in order to reduce heat input. Cryostat is made from electrical insulating materials with room temperature bore for iron core made of the commercial Fe-Si steel. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests. The AC losses were calculated and measured by calorimetric method with a mass flow meter of nitrogen gas at room temperature. The performances of the transformer in accidental cases of sudden short-circuit and lightning impulse were also tested. [ABSTRACT FROM AUTHOR]

This paper reports on the design and construction of the 100 kVA High Temperature Superconducting generator which is successfully built at the University of Southampton. The generator is a 2-pole synchronous machine with a conventional 3-phase stator and a HTS rotor which is constructed from stacks of 9 wt% Ni steel plates. The rotor winding is made of ten single vacuum impregnated pancake coils connected in series and operated in the temperature range 73-77 K. The relatively high operating temperatures are made possible by the use of metallic core as well as flux diverters between the coils. These coils have been successfully manufactured and tested over several cooling cycles. These provide the necessary mechanical support whilst minimizing the heat intake to the rotor core. The coils generate an air gap flux density of about 0.6 T at 77 K, while producing a perpendicular magnetic field of only 0.038 T to board face of the superconducting tape. Furthermore, the design and construction of two novel fiberglass torque tubes is also presented. [ABSTRACT FROM AUTHOR]

As part of the DOE-SPI funded project a commercial HTS utility-size generator is being developed based on GE's iron core superconducting generator technology. The iron core concept has significant advantages over air core designs. The rotor consists of a cold superconducting field coil and coil supports and a warm iron core, which takes the torque and transmits to the shafts. Heat load due to AC losses in the cold mass of the rotor are a key design constraint. Analyses have been performed both at the component and system levels. AC loss tests have been conducted on an HTS generator. This paper presents and discusses the analytical and test results. [ABSTRACT FROM AUTHOR]

Superconducting electrical machines are increasingly of interest for diverse applications such as generators, synchronous condensers and motors. These machines' dynamic behavior differs from that of conventional machines in significant ways due, to certain time constants and reactances being very different. These differences can present difficulties when conventional testing procedures are applied. A 5 MW superconducting rotor machine designed and built by American Superconductor Corporation is currently being tested in the Advanced Test Facility of the Center for Advanced Power Systems at Florida State University. A variety of test procedures are being applied to determine the machine's dynamic performance and the effectiveness of these tests when applied to a superconducting machine is being assessed. In this paper, two means of analysing test data and extracting machine parameters arc described. [ABSTRACT FROM AUTHOR]