High Voltage Capacitor Research Articles

Consolidation of materials by pulse-discharge processes

The article presents the research and the analysis of the pulse-discharge processes of capacitor discharge sintering: CD Stud Welding, capacitor discharge percussion welding (CDPW), high-voltage capacitor welding with an inductive-dynamic drive (HVCW with IDD), pulse electric current sintering (PECS) of powders. The comparative analysis of the impact parameter is presented.

Transient Thermal Design for Inverter Unit of High-Voltage Capacitor Charging Power Supply

In the field of electromagnetic launch or other military research, the requirements for the power density of high-voltage capacitor charging power supply (CCPS) are increasing. The design of the cooling system becomes more difficult, especially in the intermittent operation mode, when the power supply exists transient heating process. As the main heating element of CCPS, the inverter unit is the key factor to influence the power density. In this paper, the main factors that influence the temperature rise of the device are analyzed, including the material and size of the heat sink. The rules between the above factors and the transient temperature rise are analyzed by Matlab simulation software. Then, the architecture model of inverter unit is established through ICEPAK software for simulation, which proves the accuracy of the regular. A basis for designing system level power supplies working in intermittent operating mode is provided through the transient thermal design of inverter unit’D The accuracy of the rule is verified through some load short circuit experiments with a 30-kW/6 kV charging power supply.

Low dielectric loss of Bi-doped BaZr0.15Ti0.85O3 ceramics for high-voltage capacitor applications

BaZr0.15Ti0.85O3 ceramics are prepared via the conventional solid state reaction method. The effects of Bi2O3·3TiO2 doped on dielectric properties and breakdown strength of BaZr0.15Ti0.85O3 ceramics are systematically discussed. Doping of Bi2O3·3TiO2 can obviously improve the breakdown strength and reduce the dielectric loss of the material. It is attributed to the Bi3+ substituted Ba2+ is an unequal ion substitution, and two Bi3+ substitute three Ba2+ to produce an A vacancy, thereby increasing the lattice energy and promoting the diffusion and migration of the particles during the sintering process, promoting the sintering and reducing the sintering temperature. However, the dielectric constant of the material is decreased. When the amount of Bi2O3·3TiO2 is 12 mol%, the minimum dielectric loss tanδ = 0.0009, the maximum breakdown strength is Eb = 15.09 kV/mm, the insulation resistivity is 3.52 × 1011 Ω cm. The energy storage density of the BaZr0.15Ti0.85O3 ceramic samples doped with Bi2O3·3TiO2 varies from 0.008 J/cm3 to 0.012 J/cm3.

High-Resolution Time-Interleaved Eight-Channel ADC for Li-Ion Battery Stacks

An analog-to-digital converter (ADC) for monitoring the voltages of a stack of eight Li-ion batteries is presented. The converted voltage range for each battery is 3–4.2 V with a maximum nominal input voltage of 33.6 V. High-voltage (HV) switches and a single HV capacitor make up the HV track and hold. The remaining part of the circuit operates at a nominal 5-V supply. An interleaved extended-range ADC makes up the architecture. It converts the eight channels in 720 $\mu\text{s}$ . The battery monitor has been fabricated in a 0.35- $\mu\text{m}$ triple-well 5-V HV CMOS process with drain-extended MOS HV devices. The prototype active area is $1300\times 650 \mu\text{m}^{2}$ , and the measured total power consumption is 3.64 mW. The measured input-referred noise is 177.9 $\mu\text{V}$ , and the residual offset is 642.5 $\mu\text{V}$ .

Molecular adsorption at electrolyte/α-Al2O3 interface of aluminum electrolytic capacitor revealed by sum frequency vibrational spectroscopy.

The operating voltage of an aluminum electrolytic capacitor is determined by the breakdown voltage (Ub) of the Al2O3 anode. Ub is related to the molecular adsorption at the Al2O3/electrolyte interface. Therefore, we have employed sum-frequency vibrational spectroscopy (SFVS) to study the adsorption states of a simple electrolyte, ethylene glycol (EG) solution with ammonium adipate, on an α-Al2O3 surface. In an acidic electrolyte (pH < 6), the Al2O3 surface is positively charged. The observed SFVS spectra show that long chain molecules poly ethylene glycol and ethylene glycol adipate adopt a "lying" orientation at the interface. In an alkaline electrolyte (pH > 8), the Al2O3 surface is negatively charged and the short chain EG molecules adopt a "tilting" orientation. The Ub results exhibit a much higher value at pH < 6 compared with that at pH > 8. Since the "lying" long chain molecules cover and protect the Al2O3 surface, Ub increases with a decrease of pH. These findings provide new insights to study the breakdown mechanisms and to develop new electrolytes for high operating voltage capacitors.

Effects of MgO Content on Dielectric Properties of Ba0.94Bi0.04Sn0.06Ti0.94O3/MgO Composite Ceramics

The composite ceramics of Ba0.94Bi0.04Sn0.06Ti0.94O3 (BBST) with x wt.% MgO (0 ≤ x ≤ 30) were prepared by solid-state sintering. The effects of MgO content on the microstructure and dielectric properties of the composite ceramics have been investigated. The results show that MgO is uniformly distributed in BBST matrix and enhances the relative density of composite ceramics remarkably, which effectively optimizes the performances of dielectric loss, alternating current (AC) breakdown strength (BDS) and insulation. With the content of MgO increasing from 0 wt.% to 30 wt.%, the dielectric constant decreases from 2900 to 920, dielectric loss decreases from 0.011 to 0.0065, BDS is improved from 26 kV/cm to 53.6 kV/cm and leakage current density decreases from 2.96 × 10−7 A/cm2 to 9.55 × 10−8 A/cm2. The ceramic added with 30 wt.% MgO exhibits the best comprehensive dielectric properties, which is a superior dielectric used in high-voltage ceramic capacitors.

Altitude dependence of electrohydrodynamic flow in an electrostatic lifter

Experiments carried out during the last 50 years have elucidated the basic mechanism of the Biefeld-Brown effect. Recent research has focused on establishing design rules in order to maximize the lifting force resulting from this effect. For this purpose, a numerical estimation that takes the effect of altitude into account is needed. In the present contribution, the thrust due to Biefeld-Brown effect was computed by simulating the corona-discharge-induced electrohydrodynamic flow in a widely used high-voltage asymmetric capacitor with the major goal to elucidate the dependence of thrust on the altitude, pressure, temperature and humidity, respectively. Our numerical results reproduced the experimentally observed decrease of thrust with altitude and shown that this is a consequence of various competing effects.

Measurement Error Estimation for Capacitive Voltage Transformer by Insulation Parameters

Measurement errors of a capacitive voltage transformer (CVT) are relevant to its equivalent parameters for which its capacitive divider contributes the most. In daily operation, dielectric aging, moisture, dielectric breakdown, etc., it will exert mixing effects on a capacitive divider’s insulation characteristics, leading to fluctuation in equivalent parameters which result in the measurement error. This paper proposes an equivalent circuit model to represent a CVT which incorporates insulation characteristics of a capacitive divider. After software simulation and laboratory experiments, the relationship between measurement errors and insulation parameters is obtained. It indicates that variation of insulation parameters in a CVT will cause a reasonable measurement error. From field tests and calculation, equivalent capacitance mainly affects magnitude error, while dielectric loss mainly affects phase error. As capacitance changes 0.2%, magnitude error can reach −0.2%. As dielectric loss factor changes 0.2%, phase error can reach 5′. An increase of equivalent capacitance and dielectric loss factor in the high-voltage capacitor will cause a positive real power measurement error. An increase of equivalent capacitance and dielectric loss factor in the low-voltage capacitor will cause a negative real power measurement error.

Redox enhanced energy storage in an aqueous high-voltage electrochemical capacitor with a potassium bromide electrolyte

This paper reports a detailed electrochemical investigation of a symmetric carbon-carbon electrochemical device with a potassium bromide (KBr) electrolyte. Below 1.6 V, KBr gives electrochemical double layer behavior. At higher voltages the Br-/Br-3 redox reaction comes into effect and enhances the energy storage. The redox-enhanced device has a high energy density, excellent stability, as well as high coulombic and energy efficiencies even at 1.9 V. More importantly, the redox contribution can be “triggered” by pre-cycling at 1.9 V, and remains beneficial after switching to 1.6 V. The triggering operation leads to a 22% increase in stored energy with negligible sacrifice of power. The intriguing behavior is accompanied by a series of complex variations including the shifts of electrode potential limits and the shift of potential of zero voltage. The electro-oxidation of the positive electrode and kinetics of the Br-/Br-3 electrode reactions are proposed to be the main causes for the triggering phenomenon. These findings provide means to improve the design and operation of devices that contain bromine, or other redox species with a comparably high electrode potential.

DC Bus Capacitor Discharge of Permanent-Magnet Synchronous Machine Drive Systems for Hybrid Electric Vehicles

This paper investigates control methods to quickly and safely discharge the high-voltage dc bus capacitor for the permanent-magnet synchronous machine drive systems of hybrid electric vehicles during emergency situations such as a crash event. The published dc bus capacitor discharge strategies either need impractically heavy and bulky hardware or are only effective for low machine speeds. Applying the existing methods under high speeds will lead to loss of the current control and a system shutdown, followed by the bus voltage recharging again. The proposed new control method applies a modulation index controller together with a bus voltage regulator to quickly discharge the bus voltage and avoid any bus recharge regardless of the electric machine speed. Simulation and experimental results are presented to verify the effectiveness of the proposed control algorithm.

RESEARCH OF INFLUENCE OF HEIGHTENED TEMPERATURES ON THE OPERATIONAL CHARACTERISTICS OF TRANSFORMER OIL T-1500 IN FILM INSULATION SYSTEMS

The criteria parameters allowing to estimate authentically the thermostability of dielectric liquids’ operational properties are chosen. Change of transformer oil’s operational properties during its interaction with polypropylene and polyethylenetereftalate films under the influence of the heightened temperature is analysed. The influence of morphological features of polypropylene film’s surface on the thermostability of the impregnated dielectric film is revealed. Low degree of the interaction between the polyethylenetereftalate film and transformer oil T-1500 is defined.The reduction of the comparative light transmission coefficient illustrates the thermostimulated mutual dissolution in the system «polymer in the liquid». The consequent of this process is the degradation of the impregnated dielectric film components’ electrical characteristics. Analysis of kinetics of impregnating liquid’s light transmission can be informative and useful in comparative studies of various impregnated dielectric films, as well as for express diagnostics of impregnated film insulation during high-voltage pulse capacitors life tests

Improvement of resistance protection of high-voltage capacitors of powerful capacitive energy storage systems from emergency overcurrent

A resistive protection circuit of high-voltage pulse capacitors with powerful capacitive energy storage (CES) in multimodule implementation from the emergency overcurrents arising in the individual modules of CES when internal or external electric breakdown of isolation of capacitors was proposed. The main distinctive feature of this circuit is separate operation of CES modules at the stage of charging of parallel-connected capacitors and their operation together at the stage of discharge of the capacitor of modules at the total electrical load. This mode prevents the explosion-like destruction of their protective graphite–ceramic fixed resistors of TVO-60 type in an emergency arising upon breakdown of a CES capacitor at the charge stage. The calculation results of the main electrotechnical parameters of the proposed resistive protection circuit are presented. The quantitative determination of such parameters of the protective circuit of CES indicates its practical feasibility in the area of high-voltage pulse technology.

Reliability improvements of TiN/Al2O3/TiN for linear high voltage metal–insulator–metal capacitors using an optimized thermal treatment

Metal–insulator–metal (MIM) capacitors with TiN and high thickness of Al2O3 above 50 nm were fabricated to address high voltage (&amp;gt;30 V) and linear capacitor applications. Atomic layer deposition is used to deposit both TiN and Al2O3 to guarantee a good composition and thickness control. The impact of the deposition process and post-treatment condition on the MIM capacitor's breakdown voltage is studied and correlated with time of flight-secondary ion mass spectrometry (ToF-SIMS). Higher deposition temperature and thermal treatment of TiN and Al2O3 after deposition increase breakdown voltage and improve uniformity. ToF-SIMS demonstrates that Al2O3 higher deposition temperature or rapid thermal processing annealing reduce the diffusion of TiN in Al2O3 leading to thinner TiN/Al2O3 interface layers that influence breakdown voltage and uniformity.

Technologies for Prolonging Cardiac Implantable Electronic Device Longevity.

Prolonged longevity of cardiac implantable electronic devices (CIEDs) is needed not only as a passive response to match the prolonging life expectancy of patient recipients, but will also actively prolong their life expectancy by avoiding/deferring the risks (and costs) associated with device replacement. CIEDs are still exclusively powered by nonrechargeable primary batteries, and energy exhaustion is the dominant and an inevitable cause of device replacement. The longevity of a CIED is thus determined by the attrition rate of its finite energy reserve. The energy available from a battery depends on its capacity (total amount of electric charge), chemistry (anode, cathode, and electrolyte), and internal architecture (stacked plate, folded plate, and spiral wound). The energy uses of a CIED vary and include a background current for running electronic circuitry, periodic radiofrequency telemetry, high-voltage capacitor reformation, constant ventricular pacing, and sporadic shocks for the cardiac resynchronization therapy defibrillators. The energy use by a CIED is primarily determined by the patient recipient's clinical needs, but the energy stored in the device battery is entirely under the manufacturer's control. A larger battery capacity generally results in a longer-lasting device, but improved battery chemistry and architecture may allow more space-efficient designs. Armed with the necessary technical knowledge, healthcare professionals and purchasers will be empowered to make judicious selection on device models and maximize the utilization of all their energy-saving features, to prolong device longevity for the benefits of their patients and healthcare systems.

Optical Examination of Shockwave Propagation Induced by an Underwater Wire Explosion

We have been investigating underwater-explosion-induced shockwave-propagation phenomena for use in a robust food-processing system. This system comprises a high-voltage capacitor bank with gap switch, water tank, and wire explosive. We carried-out optical observation of the shockwave generated by a wire explosion using electrical discharge in the water tank. Simultaneously, we measured the shock pressure and investigated the effects of various electrical characteristics upon the shockwave-propagation phenomena. To obtain various strengths of the underwater shockwave, 0.6-, 1.0-, and 1.4-mm-wide wires made from 1.0-mm-thick aluminum plates were used at various voltages. As an example, a shockwave having a propagation velocity of 1,600 m/s was observed using the explosion of the 1.0-mm-wide aluminum wire. We found that the strength of the shockwave could be well-controlled by the discharge voltage and wire size.

Physicochemical assessment criteria for high-voltage pulse capacitors

In the paper, the applicability of decomposition products of internal insulation of high-voltage pulse capacitors is considered (aging is the reason for decomposition products of internal insulation). Decomposition products of internal insulation of high-voltage pulse capacitors can be used to evaluate their quality when in operation and in service. There have been three generations of markers of aging of insulation as in the case with power transformers. The area of applicability of markers of aging of insulation for power transformers has been studied and the area can be extended to high-voltage pulse capacitors. The research reveals that there is a correlation between the components and quantities of markers of aging of the first generation (gaseous decomposition products of insulation) dissolved in insulating liquid and the remaining life of high-voltage pulse capacitors. The application of markers of aging to evaluate the remaining service life of high-voltage pulse capacitor is a promising direction of research, because the design of high-voltage pulse capacitors keeps stability of markers of aging of insulation in high-voltage pulse capacitors. It is necessary to continue gathering statistical data concerning development of markers of aging of the first generation. One should also carry out research aimed at estimation of the remaining life of capacitors using markers of the second and the third generation.

Dielectric properties of (1-x)Sr0.84Pb0.16TiO3-xBi2O3 · 3TiO2 ceramics for high voltage capacitor application

ABSTRACT(1−x)Sr0.84Pb0.16TiO3-xBi2O3·3TiO2(SPBT) (x = 0−0.14) were synthesized by solid-state reaction method. The effects of Bi2O3·3TiO2 amount on structure of Sr0.84Pb0.16TiO3 ceramics were investigated. X-ray diffraction results reveal a pure perovskite structure for samples at x = 0-0.09, the second phase was appeared at x = 0.14. Dielectric measurements exhibit a relaxor-like characteristic for the SPBT ceramics. With addition of Bi2O3·3TiO2 the dielectric constant increases at the room temperature for x ≤ .09 and the value is above 3000 for x = 0.07 and 0.09. The average dielectric breakdown strength reaches 114.4 kV/cm and the energy storage density is 0.702J/cm3 at 10 kV/cm for x = 0.09. The Bi2O3·3TiO2 doped Sr0.84Pb0.16TiO3 ceramics had good candidate material for high voltage capacitors applications.

Trap Design and Construction for High-Power Multinuclear Magnetic Resonance Experiments.

Performing multinuclear experiments requires one or more radiofrequency (RF) coils operating at both the proton and second-nucleus frequencies; however, inductive coupling between coils must be mitigated to retain proton sensitivity and coil tuning stability. The inclusion of trap circuits simplifies placement of multinuclear RF coils while maintaining inter-element isolation. Of the commonly investigated non-proton nuclei, perhaps the most technically demanding is carbon-13, particularly when applying a proton decoupling scheme to improve the resulting spectra. This work presents experimental data for trap circuits withstanding high-power broadband proton decoupling of carbon-13 at 7 T. The advantages and challenges of building trap circuits with various inductor and capacitor components are discussed. Multiple trap designs are evaluated on the bench and utilized on an RF coil at 7 T to detect broadband proton-decoupled carbon-13 spectra from a lipid phantom. A particular trap design, built from a coaxial stub inductor and high-voltage ceramic chip capacitors, is highlighted owing to both its performance and adaptability for planar array coil elements with diverse spatial orientations.

Switched-Mode Active Decoupling Capacitor Allowing Volume Reduction of the High-Voltage DC Filters

This paper describes active shunt LC decoupling circuit with ceramic capacitors, allowing volume reduction and lifetime improvement of the high-voltage dc filters. Active filtering is based on the energy exchange between high-voltage coupling and low-voltage auxiliary capacitors. The coupling capacitor enables use of the low-voltage switched-mode power stage and low-voltage auxiliary decoupling capacitor. Advantageously, this allows to reduce power dissipation, switching frequency ripple current, and to reduce volume of the circuit. Additionally, power efficiency and capacitor lifetime are improved by using recent high-voltage coupling multilayer ceramic capacitors, reaching very low ESR. This paper provides description of the active decoupling capacitor, and shows an example of the feedback control. Obtained performances are demonstrated on the prototype of 1300-μF/450-V capacitor, allowing to reduce volume by three, when compared to ordinary 450-V electrolytic capacitor.

New Approach for High-Voltage Electrical Double-Layer Capacitors Using Vertical Graphene Nanowalls with and without Nitrogen Doping.

Integrating various devices to achieve high-performance energy storage systems to satisfy various demands in modern societies become more and more important. Electrical double-layer capacitors (EDLCs), one kind of the electrochemical capacitors, generally provide the merits of high charge-discharge rates, extremely long cycle life, and high efficiency in electricity capture/storage, leading to a desirable device of electricity management from portable electronics to hybrid vehicles or even smart grid application. However, the low cell voltage (2.5-2.7 V in organic liquid electrolytes) of EDLCs lacks the direct combination of Li-ion batteries (LIBs) and EDLCs for creating new functions in future applications without considering the issue of a relatively low energy density. Here we propose a guideline, "choosing a matching pair of electrode materials and electrolytes", to effectively extend the cell voltage of EDLCs according to three general strategies. Based on the new strategy proposed in this work, materials with an inert surface enable to tolerate a wider potential window in commercially available organic electrolytes in comparison with activated carbons (ACs). The binder-free, vertically grown graphene nanowalls (GNW) and nitrogen-doped GNW (NGNW) electrodes respectively provide good examples for extending the upper potential limit of a positive electrode of EDLCs from 0.1 to 1.5 V (vs Ag/AgNO3) as well as the lower potential limit of a negative electrode of EDLCs from -2.0 V to ca. -2.5 V in 1 M TEABF4/PC (propylene carbonate) compared to ACs. This newly designed asymmetric EDLC exhibits a cell voltage of 4 V, specific energy of 52 Wh kg(-1) (ca. a device energy density of 13 Wh kg(-1)), and specific power of 8 kW kg(-1) and ca. 100% retention after 10,000 cycles charge-discharge, reducing the series number of EDLCs to enlarge the module voltage and opening the possibility for directly combining EDLCs and LIBs in advanced applications.