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Development of Self-Healing High Temperature Film Capacitors for Power Electronics Applications

GA-ESI-Xiao Hui Yang
General Atomics Electronic Systems, Inc.-Joel Ennis, Fred MacDougall, Mark Schneider
Published 2010-11-02 by SAE International in United States
There is a need to develop improved film capacitors for high temperature, high energy density and high reliability applications. The work reported here has resulted in self-healing capacitor technology applicable to a wide variety of polymer film substrates that prevents catastrophic failures and provides safe, reliable operation in power electronic circuits. This paper describes the performance of 500-2000 Volt metalized film capacitors operating at up to 160°C under a variety of duty conditions. Data on equivalent series resistance (ESR) and power dissipation (DF), peak and Root Means Square (RMS) current ratings, and other critical performance parameters are presented. The features and benefits of both dry wrap-and-fill and liquid-impregnated hermetically sealed constructions are discussed. This work was sponsored by the US Army Research Laboratory.
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SOH Recognition of Li-ion Aviation Batteries Via Passive Diagnostic Device

Gem Power LLC-John E. James, Boris Tsenter
Published 2010-11-02 by SAE International in United States
Aviation battery maintenance is trending toward on-condition maintenance. Nickel-Cadmium (NiCd), Valve Regulated Lead-Acid (VRLA), or Lithium-Ion (Li-ion) batteries are used to start engines, provide emergency back-up power, and assure ground power capability for maintenance and pre-flight checkout. As these functions are mission essential, recognition of battery state of health (SOH) is critical. SOH includes information regarding battery energy, power and residual cycle life along with monitoring overall battery safety. This paper describes an SOH recognition technique for on-board Li-Ion aviation batteries and discusses a passive diagnostic device (PDD), that analyzes input data derived from normal system parameters such as battery current, voltage and ambient temperature. These parameters are monitored in a totally passive mode eliminating the need for active signals to the battery. Active signals are restricted or even prohibited in order to avoid any interference with the vehicle electrical system. A procedure for sampling and analyzing transient and stationary battery voltage and current and establishing a matrix of battery parameters (MoP) is discussed. The basis for SOH recognition is based on a matrix of…
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Integrated Aircraft Electrical Power System Modeling and Simulation Analysis

AFRL-Jon Zumberge, J. Wolff
PC Krause & Associates-Kevin McCarthy, Tim O'Connell, Eric Walters, Gregory Russell, Charles Lucas
Published 2010-11-02 by SAE International in United States
Advancements in electrical, mechanical, and structural design onboard modern more electric aircraft have added significant stress to the electrical systems. An electrical system level analysis tool has been created in MATLAB/Simulink to facilitate rapid system analysis and optimization to meet the growing demands of modern aircraft. An integratated model of segment level models of an electrical system including a generator, electrical accumulator unit, electrical distribution unit and electromechanical actuators has been developed. Included in the model are mission level models of an engine and aircraft to provide relevant boundary conditions. It is anticipated that the tracking of the electrical distribution through numerical integration of these various subsystems will lead to more accurate predictions of the bus power quality. In this paper the tool is used to evaluate two architectures using two different load profiles. In the first architecture conventional power resistors in the actuator electronic units are used for dissipation of regenerative energy. The second architecture makes use of a previously designed electrical accumulator unit to handle the peak and regenerative power created by the…
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Thermo-Mechanical Reliability of Nano-Silver Sintered Joints versus Lead-Free Solder Joints for Attaching Large-Area Silicon Devices

Virginia Tech-Li Jiang, Khai Ngo, Guo-quan Lu
Published 2010-11-02 by SAE International in United States
Nano-silver sintered bonding was carried out at 275°C and under 3MPa pressures, and soldering in a vacuum reflowing oven to reduce voiding. Both joints are subject to large shear stresses due to the mismatch in coefficients of thermal expansion (CTE) between the chip and the substrate. In this study, residual stresses in the chip-on-substrate assemblies were determined by measuring the bending curvatures of the bonded structures. An in-house optical setup measured the bending curvatures using a thin-film stress measurement technique. From the measured bending curvatures and the mechanical properties of the constituent materials, residual stresses were calculated. The thermo-mechanical reliabilities of both joining techniques were tested by thermal cycling. The chip assemblies were cycled between -40°C and 125°C (100 minutes of cycle time, 10 minutes of dwell time) and the changes in their bending curvatures were measured. Residual stresses were found to decrease with temperature cycling, which may be due to stress relaxation from creep or crack formation in the die-attach materials. Failure analysis of sintered nano-silver joints, eutectic Sn-3.5Ag solder (SAC305) joints and eutectic…
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Thermal Analysis of Carbon Nanotubes Suspended in PAO Mixtures

Texas A&M Univ.-Navdeep Singh, Debjyoti Banerjee
Published 2010-11-02 by SAE International in United States
Poly Alpha Olefins (PAO) are extensively used as cooling fluid for thermal management in avionics cooling applications owing to their superior physical and chemical properties, such as greater fluidity at low temperature, lower volatility, a higher viscosity index, lower pour point, better oxidative and thermal stability as well as low toxicity. Solvents doped with minute concentration of nanoparticles are termed as “Nanofluid”. Anomalous enhancements in thermo-physical property values as well as in heat transfer performance of nanofluids have been reported using nanofluids (compared to that for the neat solvent). The thermal interfacial resistance between the nanoparticle and the solvent molecules (Kapitza Resistance) is the dominant factor controlling the efficacy of the nanofluids for cooling applications. In this study Molecular Dynamics (MD) simulations were performed to estimate the interfacial thermal resistance between carbon nanotubes and surrounding fluid molecules for PAO solvent. Heat transfer from a heated (5,5) arm chair carbon nanotube to PAO molecules is explored in the simulations. The fluid molecules considered are mixtures of n-heptane, n-tridecane and n-nondecane and their isomers. The results of…
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Tracking Over Insulating Surfaces In Aerospace Environments

Univ. of Manchester-Lei Zhang, Ian Cotton
Published 2010-11-02 by SAE International in United States
As aircraft move to using higher voltages, there is an increased risk of electrical failure if clearance and creepage distances of electrical apparatus, especially printed circuit boards (PCBs) are not appropriately maintained. However, conservatism can lead to dimensions being artificially enlarged leading to significant penalties in terms of weight / volume. One failure mode that can exist on insulation of PCBs is electrical tracking across surfaces, particularly those that are contaminated (this mode of failure being distinct to arc tracking in cables). This can eventually lead to electrical failure in the form of a short circuit and could pose a fire risk in some systems. For precise dimensioning of insulation within equipment, it is necessary to understand the mechanisms of electrical tracking as influenced by different environmental conditions. Work has attempted to link the variation of pressure in an aerospace environment with the process of tracking across surfaces contaminated with an aqueous pollutant. This has been done through theoretical analysis and experimental test including the development of new test techniques that can be used in…
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Automated Model Evaluation and Verification of Aircraft Components

Lockheed Martin Aeronautics Co.-James Narey, Arthur Schuetze, Travis Clement
PC Krause and Associates-Kevin McCarthy, Brian Raczkowski, Marco Amrhein, Eric Walters
Published 2010-11-02 by SAE International in United States
The trend of moving towards model-based design and analysis of new and upgraded aircraft platforms requires integrated component and subsystem models. To support integrated system trades and design studies, these models must satisfy modeling and performance guidelines regarding interfaces, implementation, verification, and validation. As part of the Air Force Research Laboratory's (AFRL) Integrated Vehicle and Energy Technology (INVENT) Program, standardized modeling and performance guidelines have been established and documented in the Modeling Requirement and Implementation Plan (MRIP). Although these guidelines address interfaces and suggested implementation approaches, system integration challenges remain with respect to computational stability and predicted performance over the entire operating region for a given component.This paper discusses standardized model evaluation tools aimed to address these challenges at a component/subsystem level prior to system integration. These tools are analogous to component hardware acceptance testing, allow impartial and qualitative assessment of component models, and assist in determining if a component model could be successfully integrated in a subsystem- or platform-wide simulation. Further, the results provide an impartial comparison between similar components of different suppliers.Within INVENT,…
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Hardware-in-the-Loop Electric Drive Stand Issues for Jet Engine Simulation

Air Force Research Laboratory-Chad Miller, Jon Zumberge, Mitch Wolff
PC Krause & Associates-Mark Bodie
Published 2010-11-02 by SAE International in United States
Next generation aircraft will require more electrical power, more thermal cooling, and better versatility. To attain these improvements, technologies will need to be integrated and optimized at a system-level. The complexity of these integrated systems will require considerable analysis. In order to characterize and understand the implications of highly-integrated aircraft systems, the effects of pulsed-power, highly-transient loads, and the technologies that drive system-stability and behavior, an approach will be taken utilizing integrated modeling and simulation with hardware-in-the-loop (HIL). Such experiments can save time and cost and increase the general understanding of electrical and thermal phenomena as it pertains to aircraft systems before completing an integrated ground demonstration. As a first step toward completing an integrated analysis, a dynamometer “drive stand” was characterized to assess its performance. The drive stand's ability to track the low-pressure spool shaft-speed of a turbofan engine will be studied. This work will lead to understanding of the capability of the drive stand to accurately track the turbine engine low-spool speed while experiencing disturbances in the form of a torque load. It…
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Enhanced Specific Heat Capacity of Molten Salt-Metal Oxide Nanofluid as Heat Transfer Fluid for Solar Thermal Applications

Texas A&M Univ.-Donghyun Shin, Debjyoti Banerjee
Published 2010-11-02 by SAE International in United States
In this study, a molten salt-based high temperature nanofluid is explored for solar thermal energy conversion applications. The efficacy of the nanofluid as a heat transfer fluid (HTF) in concentrating solar power systems is explored in this study. The molten salt can enable higher operating temperature resulting in enhancement of the overall system efficiency for power generation (using, for example, a Rankine cycle or Stirling cycle). However, the usage of the molten salt as the HTF is limited due to their low specific heat capacity values (compared with, for example, water or silicone oils). The low specific heat of molten salt can be enhanced by doping small amount of nanoparticles. Solvents doped with minute concentration of nanoparticles are termed as "Nanofluids." Nanofluids are considered as attractive coolants for thermal management applications due to their anomalously enhanced thermal properties (compared with the neat solvent). In this study, a minute concentration of titanium dioxide nanoparticles (1% by mass) are dispersed in eutectic of chloride salts (KCl-CaCl₂-LiCl). The synthesis process involves dissolving the individual components in water followed…
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Integrated Electrical and Thermal Management Sub-system Optimization

Lockheed Martin Aeronautics-David Bodden, Bob Eller, Scott Clements
Published 2010-11-02 by SAE International in United States
Air vehicle subsystems are moving towards more electric actuation and more electric architectures. This has resulted in transient electrical power demands that require high fidelity simulations to accurately predict the peak system electrical loads. In addition, the high power electronics necessary to drive more electric system devices are generating additional heat loads, resulting in increasing demands on thermal management system performance. Consequently, integrated system simulations and the capability to optimize integrated electrical / thermal management systems are becoming necessary at earlier stages in the design cycle. LM Aeronautics has developed a MATLAB / Simulink / SimPowerSystems based toolbox for rapid modeling of thermal and electrical subsystems. Use of this toolbox for simulating and optimizing an integrated thermal / electrical subsystem is demonstrated.
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