New Considerations in the Input Filter Design of a Three-Phase Buck-Type PWM Rectifier for Aircraft Applications

An EMI filter for a three-phase buck-type medium power pulse-width modulation rectifier is designed. This filter considers differential mode noise and complies with MIL-STD-461E for the frequency range of 10kHz to 10MHz. In industrial applications, the frequency range of the standard starts at 150kHz and the designer typically uses a switching frequency of 28kHz because the fifth harmonic is out of the range. This approach is not valid for aircraft applications. In order to design the switching frequency in aircraft applications, the power losses in the semiconductors and the weight of the reactive components should be considered. The proposed design is based on a harmonic analysis of the rectifier input current and an analytical study of the input filter. The classical industrial design does not consider the inductive effect in the filter design because the grid frequency is 50/60Hz. However, in the aircraft applications, the grid frequency is 400Hz and the inductance cannot be neglected. The proposed design considers the inductance and the capacitance effect of the filter in order to obtain unitary power factor at full power. In the optimization process, several filters are designed for different switching frequencies of the converter. In addition, designs from single to five stages are considered. The power losses of the converter plus the EMI filter are estimated at these switching frequencies. Considering overall losses and minimal filter volume, the optimal switching frequency is selected.

Pre-Feasibility Study of Hybrid Wind Power-H-2 System Connected to Electrical Grid

The growth of wind power as an electric energy source is profitable from an environmental point of view and improves the energetic independence of countries with little fossil fuel resources. However, the wind resource randomness poses a great challenge in the management of electric grids. This study raises the possibility of using hydrogen as a mean to damp the variability of the wind resource. Thus, it is proposed the use of all the energy produced by a typical wind farm for hydrogen generation, that will in turn be used after for suitable generation of electric energy according to the operation rules in a liberalized electric market.

A voltage disturbances prototype for testing electrical generators connected to microgrids

The search for new energy models arises as a necessity to have a sustainable power supply. The inclusion of distributed generation sources (DG) allows to reduce the cost of facilities, increase the security of the grid or alleviate problems of congestion through the redistribution of power flows. In remote microgrids it is needed in a particular way a safe and reliable supply, which can cover the demand for a low cost; due to this, distributed generation is an alternative that is being widely introduced in these grids. But the remote microgrids are especially weak grids because of their small size, low voltage level, reduced network mesh and distribution lines with a high ratio R/X. This ratio affects the coupling between grid voltages and phase shifts, and stability becomes an issue of greater importance than in interconnected systems. To ensure the appropriate behavior of generation sources inserted in remote microgrids -and, in general, any electrical equipment-, it is essential to have devices for testing and certification. These devices must, not only faithfully reproduce disturbances occurring in remote microgrids, but also to behave against the equipment under test (EUT) as a real weak grid. This also makes the device commercially competitive. To meet these objectives and based on the aforementioned, it has been designed, built and tested a voltage disturbances generator, in order to provide a simple, versatile, full and easily scalable device to manufacturers and laboratories in the sector.

Stretching single-domain proteins: Phase diagram and kinetics of force-induced unfolding

Single-molecule force spectroscopy reveals unfolding of domains in titin on stretching. We provide a theoretical framework for these experiments by computing the phase diagrams for force-induced unfolding of single-domain proteins using lattice models. The results show that two-state folders (at zero force) unravel cooperatively, whereas stretching of non-two-state folders occurs through intermediates. The stretching rates of individual molecules show great variations reflecting the heterogeneity of force-induced unfolding pathways. The approach to the stretched state occurs in a stepwise “quantized” manner. Unfolding dynamics and forces required to stretch proteins depend sensitively on topology. The unfolding rates increase exponentially with force f till an optimum value, which is determined by the barrier to unfolding when f = 0. A mapping of these results to proteins shows qualitative agreement with force-induced unfolding of Ig-like domains in titin. We show that single-molecule force spectroscopy can be used to map the folding free energy landscape of proteins in the absence of denaturants.

Disruption of RB/E2F-1 interaction by single point mutations in E2F-1 enhances S-phase entry and apoptosis.

The retinoblastoma protein (RB) has been proposed to function as a negative regulator of cell proliferation by complexing with cellular proteins such as the transcription factor E2F. To study the biological consequences of the RB/E2F-1 interaction, point mutants of E2F-1 which fail to bind to RB were isolated by using the yeast two-hybrid system. Sequence analysis revealed that within the minimal 18-amino acid peptide of E2F-1 required for RB binding, five residues, Tyr (position 411), Glu (419), and Asp-Leu-Phe (423-425), are critical. These amino acids are conserved among the known E2F family members. While mutation of any of these five amino acids abolished binding to RB, all mutants retained their full transactivation potential. Expression of mutated E2F-1, when compared with that of wild-type, significantly accelerated entry into S phase and subsequent apoptosis. These results provide direct genetic evidence for the biological significance of the RB/E2F interaction and strongly suggest that the interplay between RB and E2F is critical for proper cell cycle progression.

Operator's and organizational maintenance manual : water purification unit, van-type, body mounted, electric driven, AC, 115, 208 V, single- and 3-phase, 60 hertz, 1/20 to 2 hp, 3000 gph (MET-PRO model 3000V), NSN 4610-00-168-1799.

"18 June 1980."

Organizational, direct support, and general support maintenance repair parts and special tools list : air conditioner, base mounted, air cooled, 208 VAC, 3-phase, 60 Hz, single package, 36,000 Btu/hr, model UAC 40-5/6-08, NSN 4120-01-122-0629, model 2643T100-1, NSN 4120-01-218-6912.

"10 October 1989."

Direct and general support and depot maintenance repair parts and special tools list : welding machine, arc, generator, electric motor driven, AC, 220V, 3 phrase [i.e. phase], 60HZ, single operator, remote control, 300 amp DC arc, wheel MTD ....

"December 1968."

Operator, organizational, field, and depot maintenance manual : welding machine, arc, generator, elec [sic] motor driven, AC, 220V, 3 phase, 60 cycle, single operator, remote control, 300 amp DC arc, wheel mounted ...

"August 1963."

Organizational, direct and general support, and depot maintenance repair parts and special tools list : air conditioner, base mounted, air cooled, 208V, 3 phase, 60 cycle, AC, single package, 36,000 BTU/HR, (York Corp model MA3-F23A), FSN 4120-926-1116.

Includes index.

Operator, organizational, direct and general support, and depot maintenance manual : air conditioner, base mounted, air cooled, 208 volt, 3-phase, 60 cycle, AC, single package, 36,000 BTU/hr, (York Corp model MA 3-F23A), FSN 4120-926-1116.

"October 1967."

Operator and organizational maintenance manual : water purification unit, van-type body mounted; electric driven, AC, 115, 208V single-and 3-phase, 60 hertz ... NS 4610-01-016-9964.

"5 March 1979."

Organizational maintenance repair parts and special tools lists : water purification unit, van-type, body mounted, electric driven, AC, 115/208 V, single and 3 phase, 60 hertz, 1/20 to 2 hp, 1500 GPH, model EMC-1500S, NSN 4610-01-037-8746.

"15 May 1980."

Operator's manual : water purification unit, base mounted, electric driven, AC, 115, 208 volt, single and 3 phase, 60 cycle, 3000 gallons per hour (MET-PRO model 3000-2700A), FSN 4610-857-0330).

"August 1963."

Direct support and general support maintenance manual : water purification unit, van type, body mounted, electric motor driven, AC, DC, 115, 208 V, single and 3 phase, 60 hertz, 1/20 to 2 hp, 1500 gph, model EMC-1500S, NSN 4610-01-037-8746, EMC Industries Inc., DAAKO1-76-C-5661.

"1 August 1979."