Joel Ennis

A three-level DC-DC converter with wide-input voltage operations for ship-electric-power-distribution systems

This paper describes a newly developed three-level dc-dc converter with wide-input voltage operations for ship-electric-power-distribution systems. The proposed converter is designed with zero-voltage-switching (ZVS) techniques. The operational principles, design details and performances of the converter are discussed along with soft-switching characteristics through experimental results. Furthermore, design criteria on the dc-dc converter are focused on the minimization of the circulation current between main switches and a transformer under soft switching. The converter has achieved about 95% efficiency over wide 7-kW load conditions.

High energy density pulsed power capacitors

Pulsed power in mobile systems requires high energy density capacitors as energy storage and power compression devices. Applications range from medical defibrillators to naval artillery, with a wide envelope of operating conditions requiring several technology approaches. The ongoing, multifaceted development effort on high energy density pulsed power capacitors at General Atomics Energy Products has yielded capacitors with significantly higher energy densities (> 5 J/cc) than were available a few years ago. Substantially higher energy densities are also being achieved in capacitors designed for microsecond discharge applications. This paper describes this progress and the state of the art in pulsed power capacitors.

Self-healing pulse capacitors for the National Ignition Facility (NIF)

Approximately 4000 capacitors, each storing 83.5 kJ of energy, will be required for the United States Department of Energy National Ignition Facility (NIF), being built at Lawrence Livermore National Laboratory (LLNL). To achieve the required system reliability lifetime, and cost goals, the capacitors were specified to be of the self-healing, metallized electrode type of construction. Maxwell Energy Products has previously delivered a number of banks of self-healing capacitors, including the 52 MJ bank at the US Army ARDEC facility at Picatinny Arsenal, NJ. Development of capacitors specifically for NIF began several years ago and continues today at Maxwell, with the primary goal of reducing the manufacturing cost. In support of this effort, LLNL has procured prototypes and life tested a number of our designs over the past three years. This paper reviews the development of NIF capacitors at Maxwell, focussing on the lifetime performance of different designs during the development. This work has resulted in Maxwell Type CM capacitor designs, whose demonstrated lifetime capability has far exceeded the 20000 shot NIF requirement, having energy densities as high as 0.84 J/cc.

High energy density capacitors for pulsed power applications

The improvement in the performance of high energy density capacitors used in pulsed power has accelerated over the past few years. This has resulted from increased research sponsored by the US Army Research Laboratory, in support of the US Militarys needs. The capacitor development effort will be discussed as well as the results of both short term and long term testing of a new generation of high energy density capacitors.

High energy density capacitors

Metallized film capacitors with energy densities as high as 3 J/cc and stored energy as high as 260 kJ per unit are now commercially available. These capacitors can be custom-designed for specific applications so as to minimize the size and weight of the capacitance for the lifetime and duty required. Applications requiring pulsed energy discharge times of 10 microseconds to 10 milliseconds are typical, but DC filtering and other types of duty can also be addressed. Packaging options include industry-standard drawn steel cans, proprietary molded plastic cases, and large welded steel cases. The performance of these capacitors as a function of voltage and size will be described.

Large High Energy Density Pulse Discharge Capacitor Characterization

The energy density of film capacitors continues to increase. This paper discusses the performance issues of limited life pulsed discharge capacitors operating at better than 2 J/cc (2 MJ/m3) in the 5 kV to 20 kV range. Self-healing metallized electrodes have been utilized in these designs to provide graceful aging at electric fields greater than 500 MV/m. A variety of polymer films have been evaluated for use in these capacitors. The pulse rise times where the capacitors find application are in the range of microseconds to milliseconds. Life tests have been performed with the goal of achieving at least 1000 charge/discharge cycles at maximum energy density. Failure modes in normal charge/discharge pulse service, and short- circuit fault conditions have been evaluated. Design modifications to increase life and energy density were made based on those analyses. Capacitors delivering greater than 100 kJ above 2 J/cc have been built, tested, and shipped.

Electrical breakdown in capacitor dielectric films: Scaling laws and the role of self-healing

Despite a great number of reports on high-energy density dielectric materials, very little attention is paid to determining realistic energy densities of larger scale devices made of these materials. These materials are typically evaluated with very short duration voltage withstand tests on very small sample areas, typically on the order of a few seconds and a few cm2. Conversely, full-scale devices require very long operational lifetimes on the order of years, and dielectric areas as large as several hundreds of m2. Practical components must also include additional material such as major insulation and packaging, resulting in volumetric efficiencies much less than 100%. Increases in total dielectric area, operating time, and packaging inefficiencies reduce practical energy densities by one to two orders of magnitude. Here we highlight the limitations of scaling up such results to high energy density capacitors as well as demonstrate the effect of self-healing and its necessity in high-energy-density, high-total-energy devices.

Design optimization of linear transformer driver (LTD) stage cell capacitors

Optimizing the design of linear transformer driver (LTD) stage capacitors is important to achieve a very low inductance and short pulse output in pulsed power generators. The stage consists of many LTD capacitor cells. The LTD performance is dependant on the characteristics of each capacitor. The capacitor construction causes distributed transmission line properties that impact the transfer of energy in terms of efficiency and time. This paper focuses on the characterization and analysis of linear transformer driver (LTD) cell capacitors in pulsed power generators using both an analytical equivalent circuit model and a SPICE simulation model. The new models of the capacitor were verified through frequency (1 MHz to 50 MHz) and time domain measurements. The measurements of the capacitors behavior provided insight for the comparison between the analytical and SPICE models. The results were matched to the models representing the capacitor. In addition, placements of tabs, connecting to capacitor windings, were characterized to determine impact on the performance of the capacitor

Custom design of components and power supplies for pulsed power systems

This paper presents an overview of custom design requirements for components and power supplies used in pulsed power systems as well as some interesting examples. Various custom design criteria for energy storage capacitors, energy-absorbing resistors, high current fuses, and capacitor charging power supplies are described. In addition, specially designed components are characterized through both simulation and experimental measurements for pulse power system applications.

Progress in the reduction of inductance in the standard 100 kV energy storage capacitor

The basic metal case low profile bushing energy storage capacitor design has changed little from the 1.85 /spl mu/F, 60 kV capacitor developed for the LANL SCYLLAC program in the late 1960s. Their enduring use testifies to a robust design. Today energy storage capacitors having a lower equivalent series inductance (ESL) will contribute to increasing the power capability of new or revised pulsed power machines. Lower ESL coupled with an improved terminal configuration for better integration with the system design, will produce faster discharge times and lower driver impedance, making higher power systems more sensible and energy efficient. A lower ESL capacitor that is compatible with existing proven hardware will also make upgrading more cost effective. This paper discusses the establishment of standardized test methods for determining the inductance of different SCYLLAC style energy storage capacitors; for example Maxwell Type C capacitors, which are now manufactured by General Atomics Energy Products, a part of Sorrento Electronics, and units from Aerovox. The effects leading to imprecision in inductance measurements will be noted. The inductance of existing designs will be compared with new hardware compatible prototype configurations with a goal of reducing the inductance up to 50%.