scholarly journals Current-pumping performance of axial-symmetric superconducting dynamo designs

2021 ◽  
Author(s):  
◽  
Sin Hoi Phang
Keyword(s):  
Liquid Nitrogen ◽  
Output Voltage ◽  
Short Circuit ◽  
Local Heating ◽  
Open Circuit ◽  
Experimental Results ◽  
Operating Frequency ◽  
Design Parameters ◽  
Dynamic Resistance ◽  
Frequency Regime

<p>In this project, the current pumping performances of three high temperature superconducting (HTS) dynamos (mechanically-rotating flux pumps) were investigated. These flux pumps (FPs) were identified as the Gen 1, Gen 2 and Gen 4 FP respectively. They were modelled using simple DC equivalent circuits and their performances were defined by three output parameters: DC open-circuit voltage (Voc), dynamic resistance (Rd) and DC short-circuit current (Isc). The experimental results showed that these FPs produced non-zero DC output voltages across their stators and each supplied DC output currents into series connected superconducting circuits.  The Gen 1 FP was cooled with liquid nitrogen and operated at 77 K. The stators were made from 12-mm wide copper-coated yttrium barium copper oxide (YBCO) HTS conductors. The objective of the experiment was to investigate the effect of the rotor magnet size, geometry and orientation (with respect to the stators) on the FP performance. The design parameters, based on the width and the length of the magnet with respect to the stator, for optimal FP performance were determined.  The Gen 2 FP was also cooled with liquid nitrogen and operated at 77 K. The stators were made from 46-mm wide Ag-coated YBCO HTS conductors. The objective of the experiment was to investigate the effect of stator width on the FP performance at various magnet frequencies. This was done by slitting two of the stators to form parallel stators with equal width, but smaller than the original conductor width. The experimental results showed that the FP performance was highly dependent on the operating frequency. Three operating frequency regimes were observed: low, mid and high. At high frequency, the Voc decreased and the Rd increased signifcantly. This was attributed to the local heating effect in the stator due to the increase in the current density. As a result, the FP produced zero output current in this regime. The AC voltage waveforms measured across the stators in different frequency regimes were very different in shapes and amplitudes. Therefore, these waveforms can be used to identify the operating frequency regime of the FP. At some operating frequencies in the mid frequency regime, bi-stable operating modes were observed, each mode resulted in different output parameters.  The Gen 4 FP was constructed in this project. It was cooled via thermal conduction method using a cryorefrigerator system. It had an axial-symmetric stator design where the shape of the stator is cylindrical. The width of the stator was considerably larger compared with the Gen 1 and Gen 2 FPs. The experiment objective was to investigate whether this design would produce a DC current, and then characterise the FP performance at different operating temperatures. The experimental results showed that the time-averaged DC output voltage of the Gen 4 FP was much higher compared with the Gen 1 and Gen 2 FPs. The reason is that it produced a DC output voltage for almost the entire rotor cycle. The experimental results also indicated that the Gen 4 FP has the capability to produce output currents in the kA range.</p>

scholarly journals Current-pumping performance of axial-symmetric superconducting dynamo designs

2021 ◽  
Author(s):  
◽  
Sin Hoi Phang
Keyword(s):  
Liquid Nitrogen ◽  
Output Voltage ◽  
Short Circuit ◽  
Local Heating ◽  
Open Circuit ◽  
Experimental Results ◽  
Operating Frequency ◽  
Design Parameters ◽  
Dynamic Resistance ◽  
Frequency Regime

<p>In this project, the current pumping performances of three high temperature superconducting (HTS) dynamos (mechanically-rotating flux pumps) were investigated. These flux pumps (FPs) were identified as the Gen 1, Gen 2 and Gen 4 FP respectively. They were modelled using simple DC equivalent circuits and their performances were defined by three output parameters: DC open-circuit voltage (Voc), dynamic resistance (Rd) and DC short-circuit current (Isc). The experimental results showed that these FPs produced non-zero DC output voltages across their stators and each supplied DC output currents into series connected superconducting circuits.  The Gen 1 FP was cooled with liquid nitrogen and operated at 77 K. The stators were made from 12-mm wide copper-coated yttrium barium copper oxide (YBCO) HTS conductors. The objective of the experiment was to investigate the effect of the rotor magnet size, geometry and orientation (with respect to the stators) on the FP performance. The design parameters, based on the width and the length of the magnet with respect to the stator, for optimal FP performance were determined.  The Gen 2 FP was also cooled with liquid nitrogen and operated at 77 K. The stators were made from 46-mm wide Ag-coated YBCO HTS conductors. The objective of the experiment was to investigate the effect of stator width on the FP performance at various magnet frequencies. This was done by slitting two of the stators to form parallel stators with equal width, but smaller than the original conductor width. The experimental results showed that the FP performance was highly dependent on the operating frequency. Three operating frequency regimes were observed: low, mid and high. At high frequency, the Voc decreased and the Rd increased signifcantly. This was attributed to the local heating effect in the stator due to the increase in the current density. As a result, the FP produced zero output current in this regime. The AC voltage waveforms measured across the stators in different frequency regimes were very different in shapes and amplitudes. Therefore, these waveforms can be used to identify the operating frequency regime of the FP. At some operating frequencies in the mid frequency regime, bi-stable operating modes were observed, each mode resulted in different output parameters.  The Gen 4 FP was constructed in this project. It was cooled via thermal conduction method using a cryorefrigerator system. It had an axial-symmetric stator design where the shape of the stator is cylindrical. The width of the stator was considerably larger compared with the Gen 1 and Gen 2 FPs. The experiment objective was to investigate whether this design would produce a DC current, and then characterise the FP performance at different operating temperatures. The experimental results showed that the time-averaged DC output voltage of the Gen 4 FP was much higher compared with the Gen 1 and Gen 2 FPs. The reason is that it produced a DC output voltage for almost the entire rotor cycle. The experimental results also indicated that the Gen 4 FP has the capability to produce output currents in the kA range.</p>

scholarly journals Understanding Photovoltaic Cell Dynamic Resistance Behavior with Changing Incident Light Intensity - draftv1.pdf

2019 ◽  
Author(s):  
FRANCISCO J. GARCIA-SANCHEZ
Keyword(s):  
Equivalent Circuit ◽  
Cell Model ◽  
Short Circuit ◽  
Incident Light ◽  
Photovoltaic Cell ◽  
Open Circuit ◽  
Photovoltaic Device ◽  
Dynamic Resistance ◽  
Analytic Expressions ◽  
Static Conditions

A theoretical examination of the general behavior that should be expected to be displayed by the magnitude of the dynamic resistance of a conventional illuminated photovoltaic device within the power-generating quadrant of its <i>I-V</i> characteristics, when measured in quasi-static conditions from the short-circuit point to the open-circuit point, at various incident illumination intensities. The analysis is based on assuming that the photovoltaic device in question may be adequately described by a simple conventional d-c lumped-element single-diode equivalent circuit solar cell model, which includes significant constant series and shunt resistive losses, but lacks any other secondary effects. Using explicit analytic expressions for the dynamic resistance, we elucidate how its magnitude changes as a function of the terminal variables, the incident illumination intensity and the model’s equivalent circuit elements’ parameters.

scholarly journals A Green Triboelectric Nano-Generator Composite of Degradable Cellulose, Piezoelectric Polymers of PVDF/PA6, and Nanoparticles of BaTiO3

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 506 ◽  
Author(s):  
Zhuangzhi Sun ◽  
Lu Yang ◽  
Sicheng Liu ◽  
Jintao Zhao ◽  
Zhiwei Hu ◽  
...  
Keyword(s):  
Polyvinylidene Fluoride ◽  
Output Voltage ◽  
Short Circuit ◽  
Open Circuit ◽  
Regenerated Cellulose ◽  
Cellulose Membrane ◽  
Output Current ◽  
Pure Cellulose ◽  
Circuit Output ◽  
Peak Value

In this paper, a kind of green triboelectric nano-generator based on natural degradable cellulose is proposed. Different kinds of regenerated cellulose composite layers are prepared by a blending doping method, and then assembled with poly(tetrafluoroethylene) (PTFE) thin films to form tribioelectric nanogenerator (TENG). The results show that the open circuit output voltage and the short circuit output current using a pure cellulose membrane is 7.925 V and 1.095 μA. After adding a certain amount of polyamide (PA6)/polyvinylidene fluoride (PVDF)/barium titanate (BaTiO3), the open circuit output voltage peak and the peak short circuit output current increases by 254.43% (to 20.155 V) and 548.04% (to 6.001 μA). The surface morphology, elemental composition and functional group of different cellulose layers are characterized by Scanning Electronic Microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and tested by the electrochemical analyze. Moreover, after multiple assembly and rectification processing, the electrical output performance shows that the peak value of open-circuit output voltage and the peak value of short circuit output current increases by 132.06% and 116.13%. Within 500 s of the charge-discharge test, the single peak charge reached 3.114 V, and the two peak charges reached 3.840 V. The results demonstrate that the nano-generator based on cellulose showed good stability and reliability, and the application and development of natural biomaterials represented by cellulose are greatly promoted in miniature electronic sensing area.

scholarly journals Design and Analysis of Gallium Nitride-Based p-i-n Diode Structure for Betavoltaic Cell with Enhanced Output Power Density

Micromachines ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1100
Author(s):  
Young Jun Yoon ◽  
Jae Sang Lee ◽  
In Man Kang ◽  
Jung Hee Lee ◽  
Dong Seok Kim
Keyword(s):  
Gallium Nitride ◽  
Power Density ◽  
Output Power ◽  
Computer Aided Design ◽  
Short Circuit ◽  
Reverse Current ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Design Parameters ◽  
Trap States

In this work, Gallium Nitride (GaN)-based p-i-n diodes were designed using a computer aided design (TCAD) simulator for realizing a betavoltaic (BV) cell with a high output power density (Pout). The short-circuit current density (JSC) and open-circuit voltage (VOC) of the 17 keV electron-beam (e-beam)-irradiated diode were evaluated with the variations of design parameters, such as the height and doping concentration of the intrinsic GaN region (Hi-GaN and Di-GaN), which influenced the depletion width in the i-GaN region. A high Hi-GaN and a low Di-GaN improved the Pout because of the enhancement of absorption and conversion efficiency. The device with the Hi-GaN of 700 nm and Di-GaN of 1 × 1016 cm−3 exhibited the highest Pout. In addition, the effects of native defects in the GaN material on the performances were investigated. While the reverse current characteristics were mainly unaffected by donor-like trap states like N vacancies, the Ga vacancies-induced acceptor-like traps significantly decreased the JSC and VOC due to an increase in recombination rate. As a result, the device with a high acceptor-like trap density dramatically degenerated the Pout. Therefore, growth of the high quality i-GaN with low acceptor-like traps is important for an enhanced Pout in BV cell.

Understanding Photovoltaic Cell Dynamic Resistance Behavior with Changing Incident Light Intensity - draftv1.pdf

2019 ◽  
Author(s):  
FRANCISCO J. GARCIA-SANCHEZ
Keyword(s):  
Equivalent Circuit ◽  
Cell Model ◽  
Short Circuit ◽  
Incident Light ◽  
Photovoltaic Cell ◽  
Open Circuit ◽  
Photovoltaic Device ◽  
Dynamic Resistance ◽  
Analytic Expressions ◽  
Static Conditions

A theoretical examination of the general behavior that should be expected to be displayed by the magnitude of the dynamic resistance of a conventional illuminated photovoltaic device within the power-generating quadrant of its <i>I-V</i> characteristics, when measured in quasi-static conditions from the short-circuit point to the open-circuit point, at various incident illumination intensities. The analysis is based on assuming that the photovoltaic device in question may be adequately described by a simple conventional d-c lumped-element single-diode equivalent circuit solar cell model, which includes significant constant series and shunt resistive losses, but lacks any other secondary effects. Using explicit analytic expressions for the dynamic resistance, we elucidate how its magnitude changes as a function of the terminal variables, the incident illumination intensity and the model’s equivalent circuit elements’ parameters.

Influence of Multiple Piezoelectric Effects on Piezoelectric Coefficient of Piezoelectric Ceramics

2011 ◽  
Vol 101-102 ◽  
pp. 922-925 ◽  
Author(s):  
Zhong Hua Zhang ◽  
Guang Ming Cheng ◽  
Jun Wu Kan ◽  
Ping Zeng ◽  
Jian Ming Wen
Keyword(s):  
Boundary Condition ◽  
Theoretical Analysis ◽  
Experimental Validation ◽  
Piezoelectric Coefficient ◽  
Short Circuit ◽  
Piezoelectric Ceramics ◽  
Open Circuit ◽  
Experimental Results ◽  
Experimental Result ◽  
Piezoelectric Effects

In this paper, theoretical analysis is performed on the influence of multiple piezoelectric effects on piezoelectric coefficients. And a kind of classical piezoelectric ceramics was adopted to conduct the experimental validation. The experimental results of short-circuit boundary condition are obtained by the methods that a capacitor whose capacitance is much larger than that of the stack is parallel with PZT-5. Influence results are obtained through comparing them with open-circuit piezoelectric coefficient. Experimental result shows that multiple piezoelectric effects make piezoelectric coefficient of PZT-5 be altered by 18%.

Influence of design parameters on inductances of e-core axial field flux-switching permanent magnet machines

2016 ◽  
Vol 35 (2) ◽  
pp. 493-506 ◽  
Author(s):  
Zhang Wei ◽  
Lin Ming Yao
Keyword(s):  
Permanent Magnet ◽  
Fault Tolerant ◽  
Short Circuit ◽  
Open Circuit ◽  
Design Parameters ◽  
Axial Field ◽  
Content Type ◽  
Copper Loss ◽  
Tooth Width ◽  
Rotor Pole

Purpose – Axial field flux-switching permanent magnet machine (AFFSPMM) can be applied in the field of electric and hybrid electric vehicles because of short axial size, large torque density, and high-power density. The purpose of this paper is to improve the reliability of AFFSPMM itself, the design parameters have to be considered for attaining high self-inductances and reduced mutual-inductances. Design/methodology/approach – The original parameters of E-core AFFSPMM are designed with reference to a 600 W prototype, on the basis of which the 3-D model of the original AFFSPMM is established, and the inductances are calculated by finite element method. The influence of these parameters on the inductances, including combinations of stator and rotor pole numbers, spilt ratio, stator side tooth width, magnet thickness, and rotor pole width etc., are respectively investigated and analyzed under the constant copper loss. Findings – The relationships of rotor pole numbers and inductances are deduced on the condition of the fixed stator poles. It is found that the rotor pole numbers has significant effects on the ratio of mutual-inductance to self-inductance, and the self-inductance is mainly affected by the rotor pole numbers, the split ratio, the stator tooth width, and the rotor pole width. The asymmetry of back-EMF can be largely reduced by optimizing the rotor tooth width. In this paper, the static characteristics are compared and analyzed for the original and optimal 6/14-pole AFFSPMM. Meanwhile, the open-circuit and short-circuit fault are investigated by transient analysis. The results show that the optimized E-core AFFSPMM has good fault tolerance. Originality/value – The research of inductance characteristics for E-core AFFSPMM is valuable to design the fault-tolerant machine, by which the cost of control and manufacture can be largely saved.

scholarly journals Understanding Photovoltaic Cell Dynamic Resistance Behavior with Changing Incident Light Intensity - draftv1.pdf

2019 ◽  
Author(s):  
FRANCISCO J. GARCIA-SANCHEZ
Keyword(s):  
Equivalent Circuit ◽  
Cell Model ◽  
Short Circuit ◽  
Incident Light ◽  
Photovoltaic Cell ◽  
Open Circuit ◽  
Photovoltaic Device ◽  
Dynamic Resistance ◽  
Analytic Expressions ◽  
Static Conditions

A theoretical examination of the general behavior that should be expected to be displayed by the magnitude of the dynamic resistance of a conventional illuminated photovoltaic device within the power-generating quadrant of its <i>I-V</i> characteristics, when measured in quasi-static conditions from the short-circuit point to the open-circuit point, at various incident illumination intensities. The analysis is based on assuming that the photovoltaic device in question may be adequately described by a simple conventional d-c lumped-element single-diode equivalent circuit solar cell model, which includes significant constant series and shunt resistive losses, but lacks any other secondary effects. Using explicit analytic expressions for the dynamic resistance, we elucidate how its magnitude changes as a function of the terminal variables, the incident illumination intensity and the model’s equivalent circuit elements’ parameters.

scholarly journals A study on performances of carrier-based pulse-width modulation techniques for three-phase three-level t-type neutral-point-clamped inverter under switch-open-circuit fault on two neutral-point-connected legs

2020 ◽  
Vol 3 (3) ◽  
pp. first
Author(s):  
Nhờ Văn NGUYỄN ◽  
HONG-PHONG NGUYEN LE
Keyword(s):  
Pulse Width ◽  
Output Voltage ◽  
Pulse Width Modulation ◽  
Short Circuit ◽  
Harmonic Distortion ◽  
Open Circuit ◽  
Neutral Point ◽  
Voltage Source ◽  
Voltage Source Inverters ◽  
Critical Issues

Multilevel voltage source inverters (VSIs) have been used for several decades thanks to their advantages compared with traditional two level VSI. Among various types of multilevel configuration, the T-type neutral-point-clamped VSI (3L TNPC VSI or 333-type VSI) has gained the attention in recent years. Due to the unique structure, the 333-type VSI has critical issues in reliability in operation such as switch-open-circuit (SOC) and switch-short-circuit (SSC), which lead to several unrequired issues, for instance, reduction of system performance, distorted and unbalanced output voltages and currents, or triggering the protection circuits. In some applications, the amplitude reduction and harmonics distortion of output voltages in SOC faults are not acceptable. Therefore, it is necessary to develop a pulse-width modulation (PWM) algorithm for 333-type VSI working under SOC fault which guarantees the desired output fundamental component voltage. The simultaneous SOC fault on two neutral-point-connected legs in the 333-type VSI may cause a large reduction in the output voltage. Under this circumstance, the 333-type VSI becomes an asymmetrical one called 322-type VSI. Certain studies regarding to the operation of 333-type VSI under SOC faults have been carried out. However, these studies require more semiconductor devices in order to create a redundant switching circuit. This leads to higher system cost with reduced inverter effieciency due to the additional loss. In this study, two carrier-based pulse-width modulation (CBPWM) techniques, i.e. 322-sinusoidal PWM (322-SPWM) and 322-medium offset CBPWM (322-MOCBPWM) are proposed for 322-type VSI. The proposed techniques are firstly simulated in MATLAB/Simulink and then implemented on a hardware setup. Performances of the proposed techniques are evaluated in terms of total harmonic distortion (THD) and weighted-THD (WTHD) of output voltages. Simulation results show that considering the worst output voltage under SOC fault, vBC, the proposed 322-SPWM technique could improve the THD by 40% and the WTHD by 94% compared with the uncompensated case with m=0.8. The corresponding results of 322-MOCBPWM technique are 42% and 96%, respectively. Characteristics of THD and WTHD values are also presented for demonstration the effectiveness of the proposed algorithm.

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