Short-duration Current Pulses Research Articles

Rapid estimation of lithium-ion battery capacity and resistances from short duration current pulses

Rapid onboard diagnosis of battery state of health enables the use of real-time control strategies that can improve product safety and maximize battery lifetime. However, onboard prediction of battery state-of-health is challenging due to the limitations imposed on diagnostic tests so as not to negatively affect the user experience and impede normal operation. To this end, we demonstrate a lightweight machine learning model capable of predicting a lithium-ion battery’s discharge capacity and internal resistance at various states of charge using only the raw voltage-capacity time-series data recorded during short-duration (100 s) current pulses. Tested on two battery aging datasets, one publicly available and the other newly collected for this work, we find that the best models can accurately predict cell discharge capacity with an average mean-absolute-percent-error of 1.66%. Additionally, we quantize and embed the machine learning model onto a microcontroller and show comparable accuracy to the computer-based model, further demonstrating the practicality of on-board rapid capacity and resistance estimation.

Depinning of the transverse domain wall trapped at magnetic impurities patterned in planar nanowires: Control of the wall motion using low-intensity and short-duration current pulses

Understanding and controlling of domain wall motion in magnetic nanowires is extremely important for the development and production of many spintronic devices. It is well known that notches are able to pin domain walls, but their pinning potential strength are too strong and it demands high-intensity current pulses to achieve wall depinning in magnetic nanowires. However, traps of pinning can be also originated from magnetic impurities, consisting of located variations of the nanowire’s magnetic properties, such as exchange stiffness constant, saturation magnetization, anisotropy constant, damping parameter, and so on. In this work, we have performed micromagnetic simulations to investigate the depinning mechanism of a transverse domain wall (TDW) trapped at an artificial magnetic defect using spin-polarized current pulses. In order to create pinning traps, a simplified magnetic impurity model, only based on a local reduction of the exchange stiffness constant, have been considered. In order to provide a background for experimental studies, we have varied the parameter related to the pinning potential strength of the magnetic impurity. By adjusting the pinning potential of magnetic impurities and choosing simultaneously a suitable current pulse, we have found that it is possible to obtain domain wall depinning by applying low-intensity and short-duration current pulses. Furthermore, it was considered a planar magnetic nanowire containing a linear distribution of equally-spaced magnetic impurities and we have demonstrated the position control of a single TDW by applying sequential current pulses; that means the wall movement from an impurity to another.

Automatic Meter Reading using Power Line Signaling and Voltage Zero-crossing Detection

In India, the electric power transmission and distribution loss is very high, about 7% in transmission and 26% in distribution. Though deployment of automated meter reading system will reduce losses, particularly in distribution, penetration of automated meter reading is low due to high costs involved. World over, the Two-Way Automatic Communications System (TWACS) is the most widely used power line communications technology offering two-way communication between substation and end users. The TWACS introduces disturbance on the power system voltage for short durations near zero-crossing to generate the outbound (from substation to end user) signal. To generate the inbound (from end user to substation) signal, short duration current pulses are introduced, near voltage zero-crossings. Information is generated as a sequential combination of voltage disturbances for the outbound signal and current pulses for the inbound signal. The current study proposes a low-cost modification of the TWACS to reduce voltage and current harmonics. The proposed system has been modelled and simulated using SIMULINK/SIMPOWER Systems. The simulation results show that there is a reduction in voltage harmonics from 0.84 to 0.17% and in current harmonics from 2.07 to 1.10%.

Coaxial-Cable Wound Rogowski Coils for Measuring Large-Magnitude Short-Duration Current Pulses

In this paper, the design, calibration, and performance improvement of four self-integrating Rogowski coils are presented. These coils are wound in single and double layers by a coaxial cable without its polyvinyl chloride (PVC) jacket and with air and ferrite cores. Nonuniformities due to the variation of turn density and/or core deformation are compensated by using a one-turn return loop placed inside the helical winding in the opposite direction to the pitch advancement. Oscillatory and overdamped unidirectional current waveforms up to a 7-kA peak value are generated by using different linear and nonlinear loads and impulse-current generator configurations. These large-magnitude short-duration current pulses are measured by different methods, namely, a commercial impulse-current transformer, a commercial Rogowski coil, and the four newly designed self-integrating Rogowski coils. The distortion of the measured current pulses is studied by using the lumped-element model of Rogowski coil and its termination resistance and the signal cable and its matching resistance. The optimal coil termination resistance is obtained under these impulses, and the linearity of all newly designed self-integrating Rogowski coils' output voltages is also investigated. Results reveal that the magnitudes of measurement errors for the current peak and front and tail times are very low when using ferrite cores with a low termination resistance. The trend of the results is also explained in terms of coil termination resistance, transit time, and sensitivity bandwidth.

Characteristics of Precursor-Dependent Breakdown in Helium Dielectric Barrier Discharge Jet

The generation of excited species in dielectric barrier discharge jets (DBD jets) when a dielectric substrate is present is highly time dependent and complex, sensitive to precursor addition and power. Both the DBD jets fed with pure helium (He DBD jet) and helium/methyl methacrylate (He/MMA DBD jet) show the characteristics of multiple short-duration (1-2 μs) current pulses during breakdown but contain different numbers, widths, and temporal sequence of pulses. In the He DBD jet, the short-duration pulses overlap to form a single broad current pulse, 4-16 μs long, per half-cycle, whereas with MMA, several broadened current pulses, 2-4 μs long, occur. It was observed that each short-duration current pulse corresponds with a leading ionization wave (or plasma bullet) followed by the formation of a plasma channel. However, if the time between ionization waves is small enough, the propagation of the second ionization wave is less observable. In He/MMA mixtures, the propagation of multiple ionization waves is more difficult to observe with increasing power as the time between current pulses decreases. With only helium, the time between current pulses is so short that only one leading wave can be observed. As the discharge power rises, more plasma channels with a thinner and brighter structure are formed during each voltage cycle, leading to observations of a mode change from a diffuse mode to a concentrated mode in the DBD jets.

Plastic deformation in electrical conductors subjected to short-duration current pulses

In this paper, we consider the viscoplastic response of Al 6061-T6 and Cu-102 when subjected to a combination of mechanical load and high-intensity electric current. The specimens are subjected to mechanical loading under fixed-grip and dead-load conditions; in addition, the specimen is subjected to a nearly sinusoidal current pulse (frequency 4kHz, duration ∼1ms, and intensity ∼109A/m2). The resulting temperature increase causes the yield stress to drop and enables accumulation of plastic strain. A viscoplastic model is used to simulate the process; comparisons of the simulation results to time resolved measurements of strain and temperature are used to calibrate the viscoplastic model.

Melting and crack growth in electrical conductors subjected to short-duration current pulses

In this paper, we examine the response of a crack tip in an electrically conducting material subjected to a combination of mechanical load as well as a high density electrical current. We present a detailed examination of the process of evolution of melting and ejection, as revealed by high speed photography. The critical mechanical and electrical parameters that govern crack extension are then determined for two different alloys. Finally, we present an evaluation of the phenomenon through a coupled field simulation to examine the nature of the interaction between the electric field and the thermo-mechanical response.

Melting and Cavity Growth in the Vicinity of Crack Tips Subjected to Short-Duration Current Pulses

The current-carrying conductors in an electromagnetic launcher are exposed to high currents that last for a few milliseconds. Surface cracks on the rails can generate large gradients in current in their vicinity and may result, in some instances, in localized melting and expulsion of rail material. Here, we report the results of a study in which the mechanical and electrical parameters of the process were monitored as a function of time and the evolution of melting and ejection was examined through high-speed photography.

EXPLOITING SONOLUMINESCENCE TO REALIZE A MEMS ULTRASONIC SENSOR

The design of a MEMS ultrasonic sensor has been presented that exploits the Single Bubble Sonoluminescence (SBSL) phenomenon to realize an energy transduction mechanism from acoustical to electrical domain. In the developed scheme, highly stable laser like short duration light pulses are emitted when ultrasound waves strike a thermally generated microbubble stabilized in a confined volume of 1% xenon-enriched water. The emitted light pulses are detected by an integrated profiled silicon type photodetector to generate ultrastable 100 picoseconds duration current pulses per acoustical cycle. The sensor exhibits energy amplification during the transduction process itself that is not achievable by conventional types of MEMS or non-MEMS acoustical sensors. The cylindrical sensor geometry is 650 μm in diameter and 300 μm in height and is designed to have a sensitivity of 5.56 mA/atm/cycle. The sensor can be used in applications where detection of high pressure ultrasound waves is necessary or as an ultrastable very short duration current pulse generator for use in tissue and nerve repair or microsurgery.

Strain Evolution in Metal Conductors Subjected to Short-Duration Current Pulses

The behavior of metallic materials subjected to short-duration heating resulting from the passage of high currents is investigated. Specifically, direct experimental measurements are made of the stress drop and recovery engendered by the application of a 1-ms-long current pulse that raises the temperature of the specimen to about 450 K. The experimental results are used to calibrate an adiabatic viscoplastic model describing the material behavior

Internal battery temperature estimation using series battery resistance measurements during cold temperatures

A technique has been developed to estimate the internal battery temperature ( T bat) of secondary batteries by measuring the series battery resistance ( R B) at cold ambient temperatures. Tests were performed on both lead-acid and nickel metal hydride batteries at different cold temperatures to obtain useful plots of R B versus T bat. R B was measured by using a pulse discharge circuit to apply a short-duration current pulse ( I B) directly to the battery. The test results indicated that R B not only varies with temperature but also varies with the amplitude of I B. The R B versus T bat plots were later utilized to predict T bat from R B during alternating current (AC) battery heating at cold ambient temperatures.

Thresholds for Activation of Rabbit Retinal Ganglion Cells with Relatively Large, Extracellular Microelectrodes

To investigate the responses of retinal ganglion cells (RGCs) to electrical stimulation, using electrodes comparable in size to those used in human studies investigating the feasibility of an electronic retinal prosthesis. Rabbit retinas were stimulated in vitro with current pulses applied to the inner surface with 125- and 500-mum diameter electrodes while the responses of RGCs were recorded extracellularly. Both short-latency (SL; 3-5 ms) and long-latency (LL; >/=9 ms) responses were observed after electrical stimulation within the receptive field of an RGC. With short, 0.1-ms current pulses, the threshold current for the SL cell response was significantly lower than that for the LL cell response. With long (10- to 20-ms) pulses, the threshold currents for the SL and LL cell responses were very similar. The threshold current for the SL cell response increased more steeply than did the LL cell response when the electrode was displaced from the point of lowest electrical threshold, either above or along the surface of the retina. Stimulation of an RGC axon outside of the cell's receptive field produced only an SL response. For 0.1-ms duration pulses, the threshold current for the axonal response was significantly higher than the threshold current for the SL cell response. At pulse durations > 1 ms, the thresholds were very similar. RGC responses to electrical stimulation depend on the current pulse duration and location of the stimulating electrode. For an epiretinal prosthesis, short-duration current pulses may be preferable since they result in a more localized activation of the retina.

Moving Current Filaments in Integrated DMOS Transistors Under Short-Duration Current Stress

Integrated vertical DMOS transistors of a 90-V smart power technology are studied under short-duration current pulses. Movement of current filaments and multiple hot spots observed by transient interferometric mapping under nondestructive snap-back conditions are reported. Device simulations show that the base push-out region associated with the filament can move from cell to cell along the drain buried layer due to the decrease of the avalanche generation rates by increasing temperature. The influence of the termination layout of the source field on the hot-spot dynamics is studied. Conditions for filament motion are discussed. The described mechanisms help homogenizing the time averaged current-density distribution and enhance the device robustness against electrostatic discharges.

Moving Current Filaments in Integrated DMOS Transistors Under Short-Duration Current Stress

Integrated vertical DMOS transistors of a 90-V smart power technology are studied under short-duration current pulses. Movement of current filaments and multiple hot spots observed by transient interferometric mapping under nondestructive snap-back conditions are reported. Device simulations show that the base push-out region associated with the filament can move from cell to cell along the drain buried layer due to the decrease of the avalanche generation rates by increasing temperature. The influence of the termination layout of the source field on the hot-spot dynamics is studied. Conditions for filament motion are discussed. The described mechanisms help homogenizing the time averaged current-density distribution and enhance the device robustness against electrostatic discharges.

Automatic adjustment of chopping-modulated defibrillation pulses to patient transthoracic resistance

Defibrillation of the heart requires a high amplitude short duration current pulse to be passed through large electrodes placed on the patient's chest. The current meets a virtually active resistance, which can vary in the approximate range of 25 to 180 z. As the delivered current or energy depends on the resistance, several methods have been developed to reduce or compensate its influence. For example, pre-shock resistance has been measured by a high-frequency current and the current or energy set accordingly; measurements have been made from the initial tilt and the pulse durations adjusted; and pre-shock measurements have been made by a sub-shock pulse to generate an appropriately selected constant current. A method is proposed using high-frequency chopped biphasic pulses, with pulse-width and period modulation of the elementary pulses. Patient resistance is measured with the first elementary pulse and depending on its value a modulated waveform is generated, selected by a micro-controller from a preprogrammed set. Thus the selected energy is accurately delivered to the patient. In addition, this method allows the shaping of a desired mean patient current waveform, maintaining adequate charge balance between the two phases and securing an appropriate time course of the model-derived transmembrane potential.

Stability measurements on cored cables in normal and superfluid helium

The relative stability of LHC type cables has been measured by the direct heating of one of the individual strands with a short duration current pulse. The minimum energy required to initiate a quench has been determined for a number of cables which have a central core to increase the effective inter-strand cross-over resistance. Experiments were performed in both normal helium at 4.4 K and superfluid at 1.9 K. Conductors in general are less stable at the lower temperature when measured at the same fraction of critical current. Results show that the cored-cables, even when partially filled with solder or with a `porous-metal' filler exhibit a relatively low stability at currents close to the critical current. It is speculated that the high inter-strand electrical and thermal resistance inherent in these cables may affect the stability at high currents.

Electrical stimulation of the auditory nerve. I. Correlation of physiological responses with cochlear status

The purpose of the present study was to evaluate evoked potential and single fibre responses to biphasic current pulses in animals with varying degrees of cochlear pathology, and to correlate any differences in the physiological response with status of the auditory nerve. Six cats, whose cochleae ranged from normal to a severe neural loss (<5% spiral ganglion survival), were used. Morphology of the electrically evoked auditory brainstem response (EABR) was similar across all animals, although electrophonic responses were only observed from the normal animal. In animals with extensive neural pathology, EABR thresholds were elevated and response amplitudes throughout the dynamic range were moderately reduced. Analysis of single VIIIth nerve fibre responses were based on 207 neurons. Spontaneous discharge rates among fibres depended on hearing status, with the majority of fibres recorded from deafened animals exhibiting little or no spontaneous activity. Electrical stimulation produced a monotonic increase in discharge rate, and a systematic reduction in response latency and temporal jitter as a function of stimulus intensity for all fibres examined. Short-duration current pulses elicited a highly synchronous response (latency <0.7 ms), with a less well synchronized response sometimes present (0.7–1.1 ms). There were, however, a number of significant differences between responses from normal and deafened cochleae. Electrophonic activity was only present in recordings from the normal animal, while mean threshold, dynamic range and latency of the direct electrical response varied with cochlear pathology. Differences in the ability of fibres to follow high stimulation rates were also observed; while neurons from the normal cochlea were capable of 100% entrainment at high rates (600–800 pulses per second (pps)), fibres recorded from deafened animals were often not capable of such entrainment at rates above 400 pps. Finally, a number of fibres in deafened animals showed evidence of `bursting', in which responses rapidly alternated between high entrainment and periods of complete inactivity. This bursting pattern was presumably associated with degenerating auditory nerve fibres, since it was not recorded from the normal animal. The present study has shown that the pathological response of the cochlea following a sensorineural hearing loss can lead to a number of significant changes in the patterns of neural activity evoked via electrical stimulation. Knowledge of the extent of these changes have important implications for the clinical application of cochlear implants.

The Role of Stress in Amorphous Magnetic Materials*

The internal stresses in amorphous Fe40Ni40B20 alloy have been relieved by passing short duration current pulses through the samples. Temperature dependence (100 K≤T≤250 K) of magnetisation of the sample which shows maximum relaxation of internal stresses after heat treatment, has been measured under the influence of external tensile stresses. Analysing the experimental data on the basis of spin-wave theory, it has been observed that the saturation moment, spin-wave stiffness constant and range of interaction change with the application of external stresses.

Effects of chronic spinalization on ankle extensor motoneurons. II. Motoneuron electrical properties

1. Intracellular recording and stimulation techniques were used in a comparison of electrical properties of triceps surae and plantaris motoneurons between unlesioned and 6-wk chronic spinal (L1-L2) cats. The primary analysis was restricted to 195 motoneurons with action potential heights > or = 80 mV. 2. Voltage transients resulting from short-duration current pulses (0.5 ms) were used to estimate membrane time constant (tau m) and equivalent cylinder electrotonic length (L). Although L was unchanged, tau m and the equalization phase time constant were significantly lower (17%) in motoneurons from chronic spinal preparations. Estimated total cell surface area was also reduced by 11%. The incidence of sag conductances, as judged from observations of the decay of voltage transients, increased from 3% to 29% after chronic spinalization. 3. Input resistance, as measured from either the amplitude of voltage responses to long-duration (50 ms) hyperpolarizing pulses (RinL) or from the area of the short-duration current pulse-induced voltage transients, was unchanged in the chronic spinal preparation. 4. Rheobase current was unchanged but threshold voltage (V Th) was increased in chronic spinal motoneurons. Increased V Th was not a result of membrane hyperpolarization because both mean action potential height (88 mV) and resting membrane potential (70 mV) were identical in both preparations. 5. The threshold current for action potential activation by short-duration (0.5 ms) current pulses increased 28% in chronic spinal preparations. This is consistent with the increase in V Th in the same motoneurons. 6. Measured V Th was identical to that calculated from the product of RinL and rheobase in the unlesioned preparation but was significantly larger than calculated V Th in chronic spinal preparations. This may indicate an increased incidence or magnitude of subthreshold rectification processes in motoneurons from chronic spinal preparations. These results in barbiturate-anesthetized preparations suggest that ankle extensor motoneurons are less excitable in the chronic spinal state. 7. Mean afterhyperpolarization duration was 10% shorter in motoneurons from chronic spinal preparations, whereas amplitude was unchanged. 8. Electrical properties were also compared in chronic spinal and unlesioned preparations using motoneurons with action potential heights of 60-79 mV. In these motoneurons with presumably poorer impalements there were no significant differences between unlesioned and chronic spinal preparations. 9. Ia monosynaptic excitatory postsynaptic potentials (EPSPs) recorded in the same motoneurons have decreased half-widths and rise times and increased amplitudes.(ABSTRACT TRUNCATED AT 400 WORDS)

Generation of elastic waves from line and point sources by a high-current pulse method

This paper describes a method of generating both line and point sources of acoustic emission (AE) signals by a powerful, transient Joule heating of a thin, conductive film deposited on an insulating plate or a small diameter metal wire buried inside it. Point-and line-source AE signals are generated by heating a short or a long section of thin film, respectively. The versatility of this method is demonstated by the diversity of AE signals that can be produced by simply changing the rise time, magnitude, and duration of the current pulse that provides the heating. An analysis shows that both the line and the point AE sources are of dipolar type for the case of the heated thin film. The line source resulting from an imbedded long, thin wire appears to be a two-dimensional center of dilatation. Short-duration current pulses generate a step source whose rise time is approximately equal to that of the input electrical power pulse while long-current pulses produce a linear ramp source that resembles the temperature rise of the heated conducting film or wire.