Experimental results and analysis from the 11 T Nb3Sn DS dipole

FNAL and CERN are developing a 5.5-m-long twin-aperture Nb3Sn dipole suitable for installation in the LHC. A 2-m-long single-aperture demonstrator dipole with 60 mm bore, a nominal field of 11 T at the LHC nominal current of 11.85 kA and 20% margin has been developed and tested. This paper presents the results of quench protection analysis and protection heater study for the Nb3Sn demonstrator dipole. Extrapolations of the results for long magnet and operation in LHC are also presented.Comment: 10 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

Investigation of Peak Current Density Effect on Magnesium Alloy AZ31B Foil Tensile Properties under High Density Pulsed Current

Utilization of high density energy assisted metal forming is gaining traction in recent year. By applying high energy to small local area, this method can improve metal\u27s workability with efficient energy usage. One of several methods in high density energy assisted metal forming is electricity assisted metal forming. Electric current was applied to working material in order to improve its workability while increases its temperature at the same time. But, the effect of temperature was stated as not the only driving force in case of flowing current. Troitskii and Okazaki et al. each stating that there is different mechanism than using only elevated temperature. Later, this effect was coined as electroplasticity by Conrad as he stated that electron wind force was present when electric current flowing thus promotes dislocation movement. But, the existence of electroplasticity effect itself still in open debate. Magargee observed that the electroplastic effect did not present while the material was forced cooled into room temperature while deformation. This observation making the change in flow stress and elongation appears to be only attributed to the temperature. Jordan and Kinsey in 2015 also did not observe electroplastic effect with current density at 40 A/mm². The reduction in force during initial stages was observed as function of temperature thus making the effect from electricity absent at this setup. Kinsey, Cullen, and Jordan did not observed any current effect from the induced eddy current in tension Kolsky bar experiment using high deformation rate. This mean the effect of electricity and pulsed current still open for discussion and need more investigation with different approach to properly distinguish the effect from thermal and athermal source. Several prior researches already been conducted to reproduce the electroplasticity effect. One of the recent developments was using electricity in form of pulsed-DC current to improve metal formability. Xie et al. in their research tried to distinguish thermal and athermal effect in the deformation behavior using tensile test by comparing the result from heating by electropulse and heating inside environmental chamber. The result showed that the electropulse did induced dynamic recrystallization which plays a role in reducing the flow stress. This research also supported by result from Bao et al. that also observed dynamic recrystallization while exposing pulsed current during tensile test. Li et al. strengthen the argument that pulsed current did have effect to material deformation behavior. They state that the effect is attributed from reinforcement of grain rotation, grain boundary sliding, formation of deformation twining, and dislocation sliding in bigger grain. This research aims to investigate influence of peak current density on tensile properties of AZ31B magnesium alloy thin foil. The specimen was exposed to high peak current densities to see effect of peak current on the tensile properties. Temperature maintained to be same throughout tests to minimize effect from temperature. Those conditions were achieved by changing its duty cycle to control the time average power. This approach can give better understanding to effect of peak current density for metals during uniaxial tensile test. All uniaxial tensile tests were performed on magnesium alloy JIS AZ31B with 50 μm in thickness. Three different temperature components were conducted in uniaxial tensile test, each 40 ℃, 70 ℃ and 200 ℃. For experiment in 40 ℃, the peak current density components are 200 A/mm², 400 A/mm² and 600 A/mm². In 70 ℃, the peak current density for each test is 500 A/mm², 750 A/mm² and 1000 A/mm². Lastly, for experiment in 200 ℃, the peak current density is 640 A/mm², 840 A/mm², 1360 A/mm² and 1820 A/mm². In order keep the initial working temperature same while changing the peak current density, duty cycle for each peak current density in their respective temperature component was set to be different. In uniform deformation, experiment with temperature condition 40 ℃ and 70 ℃ showing no significant different in their tensile properties. Proof stress shows similar value for different peak current density with each respective temperature component. Non-uniform deformation property for 40 ℃ shows different result for different peak current density. It is later noticed that in 40 ℃, proper control system was not applied therefore resulting in increase of temperature component during deformation. Contrast to that, 70 ℃ condition equipped with control system shows the tensile property in non-uniform deformation shows no different with changing peak current density. It is concluded that in low temperature, tensile property in uniform and non-uniform deformation did not affected by peak current density, instead solely regulated from its temperature. Contrast with prior result, tensile properties in 200 ℃ shows different trend of in both uniform and non-uniform deformation. Stress-strain curve for each peak current density shows long uniform deformation and short non-uniform deformation slope. Stress component in both uniform and non-uniform deformation showing rising value proportionate to the peak current density despite having same temperature. For fracture strain, opposite trend was observed. This result suggesting there is different deformation behavior in micro-scale. From power analysis, it is noted that power per pulse is proportionate to the current density. Higher power input will be translated to easier dislocation movement, faster diffusion and higher transient temperature. But, root mean square (rms) power showing similar value resulting in same working temperature for each condition. From this point of view, deformation mechanism for pulse current assisted tensile test can be better explained using energy balance model rather than depend on the surface temperature measurement. As mentioned before, the duty cycle was changed in order to control the working temperature. Changing the duty cycle for 200 ℃ condition was done by variating the frequency component of pulse current. Difference in frequency component of pulse current perceived to make the energy distribution in micro-scale to be distinct for each pulse condition. To achieve higher peak current density, the frequency needs to be lowered. It is suggested that in higher frequency the energy to aid dislocation movement has more uniform distribution rather than lower frequency since the pulse has more time to spread around individual grain. This really rapid dynamic transient energy distribution discrepancy makes the tensile property change with the change of peak current density wand frequency. Further investigation need to be conducted. By keeping more attention to energy budget needed to move the dislocation and observing behavior in different strain rate better understanding in the exact mechanism can be acquired.首都大学東京, 2018-09-30, 修士（工学）首都大学東

Superconducting fault current limiter application in a power-dense marine electrical system

Power-dense, low-voltage marine electrical systems have the potential for extremely high fault currents. Superconducting fault current limiters (SFCLs) have been of interest for many years and offer an effective method for reducing fault currents. This is very attractive in a marine vessel in terms of the benefits arising from reductions in switchgear rating (and consequently size, weight and cost) and damage at the point of fault. However, there are a number of issues that must be considered prior to installation of any SFCL device(s), particularly in the context of marine applications. Accordingly, this study analyses several such issues, including: location and resistance sizing of SFCLs; the potential effects of an SFCL on system voltage, power and frequency; and practical application issues such as the potential impact of transients such as transformer inrush. Simulations based upon an actual vessel are used to illustrate discussions and support assertions. It is shown that SFCLs, even with relatively small impedances, are highly effective at reducing prospective fault currents; the impact that higher resistance values has on fault current reduction and maintaining the system voltage for other non-faulted elements of the system is also presented and it is shown that higher resistance values are desirable in many cases. It is demonstrated that the exact nature of the SFCL application will depend significantly on the vessel’s electrical topology, the fault current contribution of each of the generators, and the properties of the SFCL device, such as size, weight, critical current value and recovery time

Effects of reduced-volume of sprint interval training and the time course of physiological and performance adaptations

This study sought to determine the time course of training adaptations to two different sprint interval training programmes with the same sprint: rest ratio (1:8) but different sprint duration. Nine participants (M: 7; F: 2) were assigned to 15-s training group (15TG) consisting of 4 to 6 x 15-s sprints interspersed with 2-min recovery, whereas eight participants (M: 5; F: 3) were assigned to 30-s training group (30TG) consisting of 4 to 6 30-s sprints interspersed with 4-min recovery. Both groups performed their respective training twice per week over 9 weeks and changes in peak oxygen uptake (V̇O2peak) and time to exhaustion (TTE) were assessed every 3 weeks. Additional 8 healthy active adults (M: 6; F: 2) completed the performance assessments 9 weeks apart without performing training (control group, CON). Following 9 weeks of training, both groups improved V̇O2peak (15TG: 12.1%; 30TG: 12.8%, P < 0.05) and TTE (15TG: 16.2%; 30TG: 12.8%, P < 0.01) to a similar extent. However, while both groups showed the greatest gains in V̇O2peak at 3 weeks (15TG: 16.6%; 30TG: 17.0%, P < 0.001), those in TTE were greatest at 9 weeks. CON did not change any of performance variables following 9 weeks. This study demonstrated that whilst the changes in cardiorespiratory function plateau within several weeks with sprint interval training, endurance capacity (TTE) is more sensitive to such training over a longer time frame in moderately-trained individuals. Furthermore, a 50% reduction in sprint duration does not diminish overall training adaptations over 9 weeks

Quantification of efficiency improvements from integration of battery energy storage systems and renewable energy sources into domestic distribution networks

Due to the increasing use of renewable, non-controllable energy generation systems energy storage systems (ESS) are seen as a necessary part of future power delivery systems. ESS have gained research interest and practical implementation over the past decade and this is expected to continue into the future. This is due to the economic and operational benefits for both network operators and customers, battery energy storage system (BESS) is used as the main focus of this research paper. This paper presents an analytical study of the benefits of deploying distributed BESS in an electrical distribution network (DN). The work explores the optimum location of installing BESS and its impact on the DN performance and possible future investment. This study provides a comparison between bulk energy storage installed at three different locations; medium voltage (MV) side and low voltage (LV) side of the distribution transformer (DT) and distributed energy storage at customers’ feeders. The performance of a typical UK DN is examined under different penetration levels of wind energy generation units and BESS. The results show that the minimum storage size is obtained when BESS is installed next to the DT. However, the power loss is reduced to its minimum when BESS and wind energy are both distributed at load busbars. The study demonstrates that BESS installation has improved the loss of life factor of the distribution transformer