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High-temperature, high-power capacitors are integral components being developed for high-temperature electronics to be used in aerospace, automotive, and other applications. Presently, a wide range of materials and capacitor technologies are being actively developed to address the needs of high temperature applications. Literature and experimental survey of existing materials and technologies focusing on commercially viable technologies has been made. Key parameters for characterizing and assessing capacitors have been compiled. Of the key competing capacitor technologies, including electrolytic, ceramic, polymer thin-film, and supercapacitors, none were found to be clearly superior to the others, thus requiring trade-offs between available choices. The review of these capacitors will be presented with respect to specific energy density, temperature capability, cost, ripple current capability, and failure tolerance.

Mn and/or rare earth-doped xCaTiO₃ - (1-x)CaMeO₃ dielectrics, where Me=Hf or Zr and x=0.7, 0.8, and 0.9 were developed to yield materials with room temperature relative permittivities of Εr ~ 150-170, thermal coefficients of capacitance (TCC) of ± 15.8% to ± 16.4% from -50 to 150°C, and band gaps of ~ 3.3-3.6 eV as determined by UV-Vis spectroscopy. Un-doped single layer capacitors exhibited room temperature energy densities as large as 9.0 J/cm₃, but showed a drastic decrease in energy density above 100°C. When doped with 0.5 mol% Mn, the temperature dependence of the breakdown strength was minimized, and energy densities similar to room temperature values (9.5 J/cm₃) were observed up to 200°C. At 300°C, energy densities as large as 6.5 J/cm₃ were measured. These observations suggest that with further reductions in grain size and dielectric layer thickness, the xCaTiO₃ - (1-x)CaMeO₃ system is a strong candidate for integration into future power electronics applications.

The desire of the US Department of Defense (DoD) to field new directed energy systems for a variety of applications increases daily. This desire stems from recent advances in energy storage and solid-state switch technologies, which enable researchers to make systems more compact and energy dense than ever before. While some systems can draw power from the mobile platform on which they are mounted, other systems need to operate independent of a platform and must be completely self-sufficient. The transient and repetitive operation of these directed energy systems requires that the prime energy source provide high power to intermediate energy storage devices. The ability of electrochemical energy storage devices, such as lithium-ion batteries, to source high power quickly has previously been limited. However, battery manufacturers have recently produced cells that are more power dense then previously available.

For fast rise time, high peak current pulse power applications, Silicon Carbide (SiC) is ideal due to its ability to tolerate high localized temperatures generated during switching. Several 4 mm × 4 mm SiC Gate Turn-Off thyristors (GTOs) manufactured by CREE were evaluated. Testing for individual and paired devices was performed under both single and repetitive pulsing using variable pulse duration, ring-down capacitor discharge circuit. At 150 °C, maximum single shot currents as high as 3.2 kA have been shown for single devices at a 50% pulse width of 2 μsec while parallel devices have shown a maximum of 4.4 kA at 150 °C.

This paper describes modeling and simulation technologies used to simulate the electrical systems of Army vehicles using Matlab/Simulink coupled with graphical user interface software. The models were built using Mathworks' Matlab/Simulink software in conjunction with the SimPowerSystems Toolbox, a toolkit provided by Mathworks that provides models of basic electrical components such as capacitors and inductors, in addition to more advanced components such as diodes and IGBT's. The current results of this ongoing effort are presented and discussed.

This paper analyses the behaviour of a highly-capacitive DC UAV network under fault conditions. Through simulation, the nature of overvoltage transients caused by the redistribution of stored energy following the clearance of a fault is illustrated. It is found that clearance of fault currents at or around their peak magnitude can result in substantial quantities of inductive energy being redirected into the smaller load capacitors, causing severe overvoltages across these loads. Recommendations for a protection strategy are given on the basis of the results presented, with consideration given to the use of surge arrestors to provide additional overvoltage protection to sensitive loads.

This paper describes the design, construction and testing of a dual-output power converter concept where the large components, such as the DC link capacitor and heat-sink, are shared between two actuators which are used sequentially in the deployment of aircraft landing gear. This mutual component approach combines the advantages of dual-use power converters with the flexibility of one power converter per application. Practical results of the converter operating are presented for a range of test conditions in order to validate the simulation study.

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.

The need for reduced system size and weight while increasing performance for military and commercial systems will require high-temperature electronics capable of running the actuators, high-speed motors and generators of the future. Of the many passive devices necessary to satisfy the need for a complete high temperature system, perhaps none has been more problematic than that of the capacitor, particularly for larger devices requiring values of several micro- to milli-farads. In this paper we introduce an ionic polymer metal composite (IPMC) we have recently developed that can operate well above the standard 125°C. These capacitors have the potential to meet all other typical aerospace and automotive design constraints of high reliability, robustness, and light weight as well as having additional features of being flexible, scalable, and customizable in shape.

We are developing compact converters for rapid charging of Energy Storage Capacitors for Compact Marx Generators. Compact Marx Generators have numerous applications in Pulsed Power Systems where Pulses with amplitudes of several 100kV with ns or sub-ns rise-times are needed. One example is the generation of High Power Microwaves. Initially all energy storage capacitors in a Marx generator are charged in parallel. During the so-called erection cycle, the capacitors are connected in series. The charging voltage in the parallel configuration is around 40-50kV. Rapid charging of the capacitors in the parallel configuration will enable a high pulse repetition-rate of the compact Marx generator.

In this paper a model of a three-phase inverter drive will be presented that is suitable for inclusion in a DC distribution system analysis. It will be shown that the drive can be accurately modeled on the electrical side by a capacitor, representing the bus capacitance of the inverter, in parallel with a current source. The current source consists of a DC component, corresponding to net power flow to and from the flywheel, plus high-frequency current harmonics generated by the operation of the switch-mode inverter. Closed-form expressions for the current harmonics can be derived by analyzing the AC currents in the electric machine and the switch-mode nature of the inverter, including the “dead-time” effect, and will be presented in the paper. Comparisons between edge-based and center-based pulse-width operation suggest that center-based PWM produces less harmonic content. It is shown that “dead-time” can have a significant effect on the harmonic content.

Capacitors are a pervasive technology in every military and commercial application. Millions are used in military systems and are considered a critical link and a common area of failure. Future military systems will rely on the development of pulsed power, high energy density capacitors for their successful deployment. These high performance capacitors are an enabling technology for the More Electric Aircraft (MEA), Directed Energy Weapons (DEW), DE ATAC, UCAV, and High Power Microwave (HPM) demonstration programs. The military will also benefit from advanced capacitor devices in Electronic Propulsion Power Conditioning, Space Based Laser (SBL) and Space Plane PMAD. To ensure the availability of these future high performance capacitor devices, the dielectric material development becomes crucial.

Thin barium titanate(BT), lead zirconate titanate(PZT), barium strontium titanate(BST) films are being developed for use in microelectronics, electromechanical and optoelectronic applications. Thin BaTiO3, Pb(ZrTi)O3 and (BaSr)TiO3 film capacitor devices were fabricated using RF sputtering techniques. The typical dielectric constant of these film capacitors was in the range of 300 to 1140. These film capacitors had dissipation factors between 0.2% to 0.6 % before annealing and 4-6% after annealing. The film capacitors have breakdown voltages in the range of 1×105 V/cm to 1.2×106 V/cm. The resistivity was in the range of 1010 to 1012 ohm-cm before annealing and 1013 to 1014 ohm-cm after annealing. The capacitance of films produced to-date had little dependence on frequency. Thermal cycling in the temperature range of 50 to 300°C had very limited impact on the capacitance and dissipation factor. Measurements of dielectric and material properties are reported.

This paper describes a ultra high power IGBT inverter. This inverter is the core component of a power supply intended to charge a 6.66 μF capacitor to 30kV (3kJ) in approximately 40 ms. The primary DC source voltage is approximately 500V. The topology of the IGBT inverter is an H-bridge rated at 1200V and 2400A. A step-up transformer and a rectifier bank are connected on the output of the H-Bridge. The IGBTs are high power modules made by Semikron. For compactness, the cooling fins of the modules have been removed down to the aluminum base-plate. This was possible due to the fact that the supply is only operated in short term burst mode. The inverter is controlled by Pulse Width Modulation (PWM) generated by a HC12 micro-controller made by Motorola. The micro-controller provides control flexibility for adaptation to the characteristics of the primary DC source. The IGBTs are switched at 10kHz.

The value of “ultracapacitors” (also referred to as “supercapacitors” or “electric double layer capacitors” in some literature) as an augmentation device when placed in parallel with “electrochemical” energy storage (i.e. battery) is presented in this paper. Since ultracapacitors possess unique attributes due to their higher value of energy storage density (or Joules/WattHrs per mass) compared to conventional capacitors while maintaining the peak power providing capability (to some degree) typical of conventional capacitors they may provide a near term solution in applications demanding longer battery operating life when placed in parallel. Such demands may be pronounced by the onset of More-Electric-Aircraft peak loads and “cold-crank” Auxiliary Power Unit (APU) electric-starting in demanding cold temperature environments.

This paper describes the development of a lead free, high temperature ceramic capacitor material having the base composition of (Na0.5 Bi0.5) TiO3. The goal is to modify this structure to create a material that has the relative permittivity of barium titanate with extended X7R-like properties to 250°C - an X14R. After an extensive compositional and theoretical modeling investigation a composition was selected and capacitors developed. The dielectric has a 1-kHz relative permittivity of ∼1200 with <±15% variation from -25 to +250°C and <5% loss from -55 to +250°C. These capacitors also have very low voltage coefficients, indeed they are positive at the low end of the temperature range, resulting in a combined TC-Vc capacitance variation 0%/-25% of nominal from -55 to +200°C with applied voltage stress from 20 to 260 V/mil.

A number of alternative capacitor technologies have been studied and high-temperature extruded polymer film capacitors hold the promise to meet the critical needs for temperature, energy density, reliability, cost and availability. Polymer resins capable of continuous use up to 200°C can be extruded into very thin films thereby permitting higher capacitor operating temperatures, higher energy density and improved cost structure compared to films manufactured by solvent casting processes. Studies of polymeric resins have shown that high-engineered polyetherimides show great promise for use as dielectric capacitor films. Polyetherimides can be melt extruded into thin films providing a low cost, environmentally friendly dielectric material. Discussions of the results of melt extrusion, metallization, and winding into electrostatic polyetherimide film capacitors will be given comparing and contrasting the results to other electrostatic film capacitor designs.