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Brushless alternating current generators for space auxiliary power systems - design manuals and computer programs
Scanning and transmission electron microscopy were used to characterize the morphology of the carbon microcoils (CMCs). The Raman spectra showed that CMCs had local regular structure as I{sub D}/I{sub G} = 0.841. Then, aligned CMCs/silicone–rubber composites (5 × 5 × 1 mm{sup 3}) were fabricated by coating of silicone rubber on the CMCs. Their alternating current impedance characteristics were measured as a function of applied load and the pressure sensitivity was discussed. The results showed that the impedance decreased as the increasing applied load, and the sample with less CMCs owned high pressure sensitivity, which indicated a novel composite film could act as an alternative of tactile sensor.
Most of the renewable energy sources are not distributed directly to consumer. It gone through several section to get optimum output voltage and current with the almost zero distortion. Direct Matrix converters are well known of its better power quality and low power distortion to the reactive loads. Conversely, multilevel H bridge inverters are broadly used to attain a sinusoidal output voltage in solar photovoltaic application. Reactive power is subject to high importance for the operation of alternating current (AC) power systems. Moreover there is always a challenge to obtain the balance current control from an unbalanced supply voltage with minimum harmonic distortion for reactive load application from solar power system. The main objective of the proposed system is to maximize the power usage by maintaining the current and power factor nearby unity. There are many different optimization techniques are used so far in matrix converter, a novel method of optimization BAT algorithm is proposed for the power quality to get the best result. This work mainly deals with the compensation of reactive power used in Solar Photovoltaic Power System. Bidirectional energy flow is possible with matrix converter for battery charging. Simulation results are presented to confirm the appropriate operation of the system under different of operating conditions. Also, in the proposed method the percentage of the higher order harmonics can reduced less than 9% of matrix converter for solar photovoltaic application.
More and more researchers have been attracted to the research of atmospheric pressure glow discharge (APGD) because of its great prospect in numerous industrial applications. Nevertheless, almost all of the industrial applications are based on achievement of stable, large-volume, and uniform APGD. In a previous study, stable filamentary APGD was obtained by applying a resonant power supply between pin-to-plate electrodes which could limit the peak value of discharge current to supress the glow-to-arc transition through a series-wound resonance principle. The filamentary APGD is centimeter-level in the length but only several millimeters in diameter. Therefore, in order to obtain large-volume and uniform APGD, it is significant to study how to diffuse filamentary APGD in radial direction. With the increasing resonant frequency of alternating current discharge, excited particles (mainly including energetic electrons and trapped ions left from the previous half-cycle discharge) in the electrodes gap increase, which benefits obtaining stable self-sustaining APGD. In this paper, mechanism and law of the influence of resonant frequency on the diffusion of filamentary APGD in ambient air were studied. By comparing the photos of discharge plasma and waveforms of the discharge voltage and current, it is found that the volume of the glow discharge plasma enlarges as the resonant frequency of the power supply increases. It is very significant and anticipating to study how to obtain stable, large-volume, and uniform APGD in ambient air by the resonant power supply.
The coupling effect of stray AC (alternating current) + DC (direct current) and tensile stress-induced X70 pipeline corrosion is complicated with its mechanism uncovered. In this work, the corrosion behavior of X70 pipeline steel under three different corrosion (including an individual AC corrosion, mixed AC + 150 MPa tensile stress corrosion, coupling effect of AC + a 30 A/m{sup 2} DC interference and 150 MPa tensile stress corrosion) conditions in Dagang soil simulated solution was investigated by COMSOL Multiphysics software simulation, electrochemical tests, scanning electron microscope and other techniques. The results indicated that with the increase in AC density, the open-circuit potential of the X70 steel samples was negatively shifted and corrosion rate increased in three different corrosion conditions. The corrosion rates of X70 steel samples under individual AC interference were almost unchanged when 150.9 MPa tensile stress was applied. When applying 30 A/m{sup 2} DC interference, the corrosion rate of X70 steel increases significantly. Therefore, the factors affecting corrosion performance of X70 pipeline steel were DC > AC > stress. Under individual AC interference, uniform corrosion occurred on the X70 steel at an AC current density of less than 30 A/m{sup 2}, while the pitting corrosion occurred at an AC current density of greater than 100 A/m{sup 2}. The application of tensile stress and DC had a certain inhibitory effect on pitting corrosion.
Large power electronics systems like multi-port autonomous reconfigurable solar power plant (MARS) are increasingly being researched upon to integrate emerging energy sources. MARS connects photovoltaic (PV) systems and energy storage systems (ESSs) to high-voltage direct current (HVdc) links/grids and high-voltage alternating current (ac) transmission grids. As these large power electronics systems incorporate complex hierarchical control systems that are close-by and communicate fast, the control systems require an unique power electronic hardware-in-the-loop (PE-HIL) real-time architecture to evaluate individual controllers. In this paper, a PE-HIL real-time architecture is proposed to evaluate one of the hundreds to thousands of digital signal processors (DSPs) that are a part of the complex hierarchical control system. The DSP connects to a central processing unit (CPU) and a field programmable gate array (FPGA) that form a part of the upper levels of the control system. The DSP is part of the lower level of the control system. The proposed PE-HIL architecture is tested and evaluated. Preliminary test results are presented to showcase the concept.
The direct current (dc) conductivity and emergent functionalities at ferroelectric domain walls are closely linked to the local polarization charges. Depending on the charge state, the walls can exhibit unusual dc conduction ranging from insulating to metallic-like, which is leveraged in domain-wall-based memory, multilevel data storage, and synaptic devices. In contrast to the functional dc behaviors at charged walls, their response to alternating currents (ac) remains to be resolved. Here, we reveal ac characteristics at positively and negatively charged walls in ErMnO 3 , distinctly different from the response of the surrounding domains. By combining voltage-dependent spectroscopic measurements on macroscopic and local scales, we demonstrate a pronounced nonlinear response at the electrode-wall junction, which correlates with the domain-wall charge state. The dependence on the ac drive voltage enables reversible switching between uni- and bipolar output signals, providing conceptually new opportunities for the application of charged walls as functional nanoelements in ac circuitry.
Carbothermic smelting of ores to produce metals or alloys in alternating current open/semiclosed and closed submerged arc furnaces, or in closed direct current furnaces, results in large volumes of CO-rich off-gas being generated. Most of the CO-rich off-gas is cleaned and flared on stacks, since the storing of large volumes is problematic due to the associated toxic and explosive risks. Flaring of CO-rich off-gas results in significant wastage of energy. In this study, an alternative method to partially capture the thermal energy associated with off-gas combustion, in the form of silicon carbide (SiC) generated from waste materials (quartz and anthracite fines), is proposed. SiC can partially replace conventional carbonaceous reductants used to produce alloys such as ferrochromium. The influences of quartz and anthracite particle size, treatment temperature, and gaseous atmosphere (nitrogen or air) on SiC formation were investigated. A quartz-anthracite mixture with 90 pct of the particles < 350.9 µm carbothermically treated at 1873.15 K (1600 °C) resulted in almost complete conversion of quartz to SiC in both nitrogen and air atmospheres. The study indicated significant potential for industrial application of the process.
Highlights: • Crystallinity of polythiophene decreased with doping process. • Zirconium dioxide changed the surface morphology of PT significantly. • Doping process increased the glass transition temperature of polythiophene. • Charge transport mechanism of all samples is consistent with CBH model. - Abstract: This paper reports charge transport mechanism of polythiophene (PT) and its nanocomposites having various weight of zirconium dioxide (ZrO{sub 2}). Fourier transform infrared (FT-IR) spectral studies showed that the Zr ions mostly affected the C−S bond of the polythiophene. X-ray diffraction (XRD) patterns indicated that ZrO{sub 2} powder was a mixture of monoclinic (64.62%) and tetragonal (35.38%) phase. XRD measurements revealed that crystallinity of PT decreased with increasing doping level. Significant morphological differences were observed in scanning electron microscopy (SEM) images of PT depending on the doping process. Thermal analysis carried out by differential scanning calorimetry (DSC) indicated that the doping processes increased glass transition temperature of PT. The alternating current (ac) conductivity mechanism analysis by universal power law indicated that charge transport mechanism of both PT and PT/ZrO{sub 2} nanocomposites was consistent with correlated barrier hopping (CBH) model. The doping process and frequency affected the hopping distance between the sites.
In recent study, the number of BaZrTiO{sub 3} layers were successively deposited on the Si-substrate by spin-coating process. The increasing of layers number affects the films structure which has been observed in XRD, while the ferroelectric properties have been analyzed by Sawyer-Tower. Perovskite tetragonal is observed in all films by the c-a axis ratio around 1.002 to 1.018, and the crystallite sizes were calculated from 75 nm to 129 nm. The maximum polarization value was found to be decreased during the increase of numbers of layers from 3 to 4 layers. On the contrary, the value was noticeably increased to the highest value when 5 layers film was applied. The highest maximum polarization were recorded at 31.68 µC/cm{sup 2} and 34.12 µC/cm{sup 2} respectively for 5 layer BZT films in each 8 at.% and 10 at.% Zr content under electrical fields injection as triangle signal of Alternating Current (AC) 50 V/60 Hz. As the number of layers increases, the polarization field magnitude is significantly decreased. The general results of structure and ferroelectric properties of BZT films have been studied in the influence of layers number to enhance the electrical behavior.
We demonstrate a simple device to generate chemical concentration gradients in a microfluidic channel using focused travelling surface acoustic waves (F-TSAW). A pair of curved interdigitated metal electrodes deposited on the surface of a piezoelectric (LiNbO{sub 3}) substrate disseminate high frequency sound waves when actuated by an alternating current source. The F-TSAW produces chaotic acoustic streaming flow upon its interaction with the fluid inside a microfluidic channel, which mixes confluent streams of chemicals in a controlled fashion for an adjustable and rapidly switching gradient generation.
We present a study on electrically- and spatially-controllable laser beam diffraction, electrooptic (EO) phase modulation, as well as amplitude-frequency EO modulation by single-layer microscale polymer-dispersed liquid crystal (PDLC) phase gratings (PDLC SLPGs) of interest for device applications. PDLC SLPGs were produced from nematic liquid crystal (LC) E7 in photo-curable NOA65 polymer. The wedge-formed PDLC SLPGs have a continuously variable thickness (2–25 µm). They contain LC droplets of diameters twice as the layer thickness, with a linear-gradient size distribution along the wedge. By applying alternating-current (AC) electric field, the PDLC SLPGs produce efficient: (i) diffraction splitting of transmitted laser beams; (ii) spatial redistribution of diffracted light intensity; (iii) optical phase modulation; (iv) amplitude-frequency modulation, all controllable by the driven AC field and the droplet size gradient.
An atmospheric-pressure non-thermal plasma jet driven by high frequency alternating current and operating on N{sub 2} and N{sub 2}/O{sub 2} gas mixture is investigated. The plasma jet can reach 55 mm in length at a gas flow rate of 2500 l/h. The gas temperature at a distance of 4 mm from the nozzle is close to room temperature. Optical emission spectroscopy is employed to investigate the important plasma parameters such as the excited species, rotational temperature, vibrational temperature, and excitation temperature under different discharge conditions. The results show that the plasma source operates under non-equilibrium conditions. The absolute irradiance intensity of the vibrational band N{sub 2}(C-B) in the active region is measured. Taking into account the irradiance intensity of N{sub 2}(C-B,0-0) and N{sub 2}(B-X,0-0) as well as measured current, the electron density, which is determined by considering direct and step-wise electron impact excitation of nitrogen emission, reaches a maximum value of 5.6 × 10{sup 20}/m{sup 3}.
Regarding nuclear power plant development in Bangka Island, it can be estimated that produced power will be oversupply for the Bangka Island and needs to transmit to Sumatra or Java Island. The distance between the regions or islands causing considerable loss of power in transmission by alternating current, and a wide range of technical and economical issues. The objective of this paper addresses to economics analysis of direct current transmission system to overcome those technical problem. Direct current transmission has a stable characteristic, so that the power delivery from Bangka to Sumatra or Java in a large scale efficiently and reliably can be done. HVDC system costs depend on the power capacity applied to the system and length of the transmission line in addition to other variables that may be different.
The electrical properties of R-phycoerythrin modified with Ag{sup 0} nanoparticles (Ag{sup 0} • R-PE) as a candidate material for biosensors were studied were studied. Modification was ensured by a known procedure: synthesis of Ag{sup 0} nanoparticles in R-phycoerythrin channels through the addition of AgNO{sub 3} to an aqueous R-phycoerythrin solution. According to electron microscopy results, the Ag{sup 0} • R-PE contains predominantly elongated Ag{sup 0} nanoparticles 6.2 ± 0.5 nm in length, which form structures similar to rows 20–60 nm in length. The electrical conductivity, dielectric permittivity, and dielectric loss of the Ag{sup 0} • R-PE have been measured in the frequency range from 0.01 Hz to 1 MHz. Filling the channels in R-phycoerythrin molecules with Ag{sup 0} nanoparticles has been shown to increase the alternating current electrical conductivity and dielectric loss of the material at low frequencies by more than 200 times and its dielectric permittivity by 40 times. Ag{sup 0} nanoparticles increase the direct current conductivity of R-phycoerythrin from 5 × 10{sup –14} to 2.5 × 10{sup –11} S/cm. The electrical properties of Ag • R-PE are comparable to those of conductive polymer composites that contain metallic nanowires and are used in designing multifunctional films and smart materials.
Highly aligned polyimide (PI) and PI/multi-walled carbon nanotubes (PI/MWCNTs) nanofibrous composites by incorporating poly(ethylene oxide) as the dispersing medium were fabricated using electrospinning technique. The morphology, mechanical, and electrical properties of the electrospun nanofibrous composites were investigated. Scanning electron microscope showed that the functionalized MWCNTs (f-MWCNTs) were well dispersed and oriented along the nanofiber axis. Analysis of electrical properties indicated a remarkable improvement on the alternating current conductivity by introduction of the aligned f-MWCNTs. Besides, with addition of 3 vol. % f-MWCNTs, the obvious enhancement of tensile modulus and strength was achieved. Thus, the electrospun PI/MWCNTs nanofibrous composites have great potential applications in multifunctional engineering materials.
Semiconductor quantum dots (QDs) with high fluorescent brightness, stability, and tunable sizes, have received considerable interest for imaging, sensing, and delivery of biomolecules. In this research, we demonstrate location deterministic biochemical detection from arrays of QD-nanowire hybrid assemblies. QDs with diameters less than 10 nm are manipulated and precisely positioned on the tips of the assembled Gold (Au) nanowires. The manipulation mechanisms are quantitatively understood as the synergetic effects of dielectrophoretic (DEP) and alternating current electroosmosis (ACEO) due to AC electric fields. The QD-nanowire hybrid sensors operate uniquely by concentrating bioanalytes to QDs on the tips of nanowires before detection, offering much enhanced efficiency and sensitivity, in addition to the position-predictable rationality. This research could result in advances in QD-based biomedical detection and inspires an innovative approach for fabricating various QD-based nanodevices.
This paper studies the performance of a Permanent Magnet (PM) alternating-current (AC) machine when subjected to faults under load conditions. The effect of varying load torques, and unbalances are found to be potential causes of rotor faults, inducing physical magnet defects or broken rotor-PMs. The consequent and immediate impact on the machine quantities is observed through anomalous change in torque-speed characteristics and other vital signatures such as machine back-EMF/flux and motor current signatures (MCS). The present research study develops and illustrates a method to diagnose physical magnet defects (fault) in PMAC machines by estimating the machine torque/back-EMF constant, Ke. The constant Ke is a measure of magnet strength exhibiting the health of rotor PMs, indicative of faults. Advanced research studies and investigations are carried out to establish motor approximations and signature-based analysis as significant viable tools for diagnosing machine faults even under load conditions.