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In this article, we present the theoretical models on self-healing (SH) processes in metallized film capacitors (MFCs) in overload modes. Based on the proposed dynamic model of capacitor’s SH resistance, the current and voltage of MFC in SH process and the value of dissipated energy, $W_{\text {SH}}$ , can be calculated. Theoretical model of MFC degradation due to SH processes approves that in the vicinity of the breakdown places of polymer dielectric, a high SH energy leads to their carbonization. The numerous SH events result in the decreasing of the equivalent parallel resistance (EPR). An analysis of MFC electrothermal state shows that at critical values of applied voltage at 4–5 of nominal values, the dangerous local heating of the polymer dielectric can occur. Computer simulation describes the behavior of the EPR of the polymer film capacitor, which is determined by the number and intensity of SH acts. Finally, the numerical model for evaluation of the thermal state of the capacitor is offered. Numerous SH acts (especially of high SH energy level) cause the local heating of MFC section. The surface temperature of the capacitor may seem normal, though the local heating reaches the level dangerous for polymer. The analytic estimations and simulation results are in quite good agreement with experimental data.

Metallized film capacitors (MFCs) are used in many applications requiring high volumetric energy characteristics. Along with an increase in the dielectric permittivity of the polymer film, operating in overload mode is a simple way to dramatically increase the energy density of capacitors for relatively short periods. The unique feature of MFC, a self-healing (SH) ability, makes this possible. However, the task is complicated by the lack of information on the energy characteristics of SH in real capacitors, especially when they are voltage overstressed. Part 1 of this article contains the results of experimental investigations of SH processes in overload modes under the soft-training test. At the level of voltage up to 8 of nominal values, three types of SH were discovered: single, repetitive, and multiple. The energy characteristics of SH processes obtained in real MFCs varied widely from those in the literature data. The cumulative SH energy characteristic was introduced and proposed for diagnostic purposes. The reasons for repetitive SH were investigated and analyzed. Equivalent parallel resistance as a sensitive diagnostic parameter of the overloaded MFC was chosen and applied.

Polymer film capacitors are widely used in modern power equipment, because of excellent volumetric characteristics in combination with high-voltage application ability. Using segmented electrodes of nanometer thickness increased the capacitor’s performance and reliability because of the self-healing feature. In this paper, we present the results of the experimental investigation and numerical simulation of electrothermal destruction of the metallized film capacitors segmented electrodes during the self-healing process. The destruction processes were investigated for both a single gate and single segment, comprising four parallel gates connected to the segment. The numerical simulation was conducted by means of COMSOL Multiphysics software. The model takes into account the heat flow from metal layer to polymer film since it has significant influence on the destruction process. Based on a good agreement of experimental and numerical results, the simulation model was proposed for the real metallized film capacitor segmented electrodes design. The model allows evaluating the single segment isolating time during self-healing, the energy required for the isolating, effective value of segmented electrodes surface resistance.

Current-induced defects were observed in segmented electrodes of metallized film capacitors. Aperiodical current pulses of different amplitude and duration were applied to the experimental samples. It was found that thin demetallized lines (cracks) propagate in the direction of current streamlines. Scanning electron microscope was used to determine a width of investigated defects. Current density value needed to demetallized lines appear was calculated using numerical simulation in COMSOL Multiphysics software. It was proved that these defects are fast electromigration cracks.

The influence of Al and Zn metallization and demetallization processes on breakdown strength of thin polypropylene film is investigated. The breakdown strength of a polypropylene film drops about 10% upon covering with thermally evaporated 10 to 50 nm thick Al metallization, and it weakly depends on the thickness of metal layer. Al form nanoparticles 10-20 nm in size over polypropylene fibers at the initial stage of metallization layer formation. These nanoparticles grow and coalesce with Al layer thickness increase. The demetallization by the electric explosion and surface arc discharge induced erosion of metal layer (aluminum or zinc) process leads to up to 30% reduction of breakdown strength for aluminum metallization, and up to 20% for zinc metallization, respectively.

The article describes a technique for calculating the thermal conductivity coefficient of the insulation system. The technique was applied for evaluating new design solutions, developing corrective proposals for optimizing the insulation system design, including the employment of highly heat-conducting materials. The developed tools allow to accelerate the developing process of insulation systems, increase the reliability of the results obtained within introducing new insulation systems, reveal the key elements of the insulation system that determine the possibility of effective increasing heat transfer in the stator winding insulation system of turbo- and hydro-generators.

The novel types of electrodes segmentation patterns for metallized film capacitors were suggested. Electrodynamic destruction of segmented electrodes due to self-healing process was numerically calculated using COMSOL Multiphysics software. The dependence of electrodynamic destruction energy versus destruction time was used as a criterion of segmentation pattern efficiency. Advantages and disadvantages of novel electrodes segmentation types were determined. It was found that bridge-diamond segmentation is the most effective patterns configuration.

A typical approach to minimizing the early failures (“infant mortality”) of the modern metallized film capacitors (MFCs) is to conduct a burn-in test at applied voltage slightly more (at 30 – 50%) than nominal value. During the test, an external capacitor bank is used as a capacitive storage device with an energy significantly exceeding the energy level of the capacitor under the test. Thus, the amount of energy in the self-healing (SH) process is practically unlimited, which may lead to catastrophic failure of the capacitor. Recently, the soft training test for application of such capacitors in overload modes has been proposed. This can significantly improve the MFCs technical characteristics. We present the results of experimental and theoretical study on SH processes of MFCs in soft training test, allowing the capacitors to operate at voltages 3 – 5 times higher than nominal value. The MFC’s degradation is associated with the equivalent parallel resistance (EPR) decreasing due to numerous SH events. On the base of the developed physical model, the relationship between critical value of testing voltage and EPR as a diagnostic parameter is offered.

The influence of metallized polypropylene demetallization processes, such as an electric explosion of metal layer and metal evaporation due to surface arc discharge, was investigated. 6 $\mu$ m thick polymer film with aluminum and zinc metallization were tested. It was found that electric explosion and surface arc impact on polymer surface cause 20 and 30 percent reduction of breakdown strength for aluminum metallization, and 14 and 21 percent for zinc metallization, respectively. The results are useful for choosing the parameters of MFC voltage overstressing regimes.

One of the main reasons of metal film capacitors failure in pulse modes is a degradation of contacts between film metallization and solid electrodes—contact edges. This paper presents the results of experimental investigations of modeled contact edges behavior under current pulses of varying amplitude, duration, and quantity. It was found that the contact edge degradation is caused only by metallization destruction and independent on metal of the solid electrodes (“shoopage”). Depending on pulse parameters and dissipated energy in the contact edge, the contact erosion rate is in the range of (0.4– $2.7) \times 10^{-3}$ g/J. Current pulse polarity effect on contact edge degradation was found: mean time to failure (MTTF) of the contact edge depends on its polarity, i.e., on the direction of the current flow through the contact during charge or discharge of capacitor. For different contacts polarities the difference between MTTFs reaches 20%–60% depending on pulse parameters. Based on these facts, one makes a supposition that the timely changing of the capacitor’s terminals polarity can lead to the increasing of capacitor lifetime.

Numerical simulation of metal-film capacitors segmented electrodes was conducted. Conventional segmentation with intersegment bridges and novel hybrid segmentation were simulated and compared with all-over metallized electrodes. The calculated characteristics are: surface resistance of the electrodes active area of the electrodes resulting in overall capacitance, current density distribution. It was established that surface resistance of hybrid-segmented metallization is much lower than one of bridge-patterned, and close enough for all-over metallization. The hybrid-segmented electrodes were found to be less overloaded by current.

The experimental investigation of the characteristics of vibration sparking in HV rotating machine insulation was carried out. For this purpose, special experimental setup was developed. It allowed to vary the vibration gap, gap voltage and current in the range of 10-200 um, 5-300 V, 0.1-100 mA respectively. Corona protection materials were investigated. Their VI characteristics were obtained and compared. Comsol Multiphysics software was used for numerical simulation of electrophysical processes in electric insulation and corona protection layers. Recommended surface resistance of corona protection materials for avoiding vibration sparking was evaluated based on experimental and simulation results.

The goal of the paper is testing the short-pulse dielectric strength of chip capacitors and lightning impulse testing with subsequent failure analysis. The experimental setups are developed in order to determine the short-pulse dielectric strength and lightning impulse withstand voltage. The distribution functions of these characteristics have been found to follow the normal distribution. The oscillograms of current and voltage across the capacitors during the tests are presented. A brief failure analysis is carried out. The main failure mechanisms are highlighted. The obtained results will be the basis for the method of preliminary estimation of short-pulse dielectric strength in chip capacitors.

The main purpose of this work is numerical investigation of HV rotating machine insulation system. Comsol Multiphysics software was used to develop the model of Resin Rich based insulation system. The numerical simulation of electrophysical processes in insulation was conducted. The influence of insulation components’ electric properties on electric field distribution was studied. The recommended range of resistivity for minimization of electric field in air gaps was obtained. The breakdown possibility due to different kinds of insulation defects was evaluated.

The multilayer ceramic capacitors’ (MLCC) performance under high ac loads was studied. The mean time to failure (MTTF) of MLCCs’ depending on voltage across the capacitor was established. It was found that MTTF follows the power law. The temperature spectra of capacitance and dissipation factor were obtained. Numerical simulation by means of Comsol Multiphysics was conducted showed unsuitability of small signal characteristics to evaluate capacitor’s performance under high loads.

Metallized film capacitors are prospective for using in pulsed power techniques because of their high values of energy density. During the microsecond timescale discharges the high currents may cause the electrothermal destruction of the continuous connection between metallization and plasma sprayed end, making it fragmentary. In this case the strong frequency dispersion of capacitance can appear that was observed experimentally before. The model of the capacitance frequency dispersion is offered. The obtained exact analytic solutions provide good agreement with the numerical simulations using frequency-domain finite element analysis by Comsol Multiphysics software.

Operation of metallized film capacitors in high current overload mode was experimentally studied. Changes in frequency spectra of capacitance and dissipation factor were revealed. It was found that effective capacitance rapidly decreases in the high frequency region (more than 1 kHz). The dissipation factor monotonie increasing and appearance of peaks in its frequency dependence were also found. Numerical modeling results showed that changing in frequency dependencies of capacitance and dissipation factor is due to contact edges degradation and following non-uniform distribution of electric potential in the vicinity of capacitor's electrodes. Based on experimental and calculation dataset the equivalent circuit of metallized film capacitor was proposed. This circuit takes into account degradation of electrodes during overload mode operating.

We present the experimental results of the nanometer Zn films electrical explosion in the air. The film destruction is accompanied with the stratification; the strata are formed in the transverse direction to the applied electric field. The initial strata growth can be explained by the electro-thermal instability development. The strata propagation velocity reaches 50 km/s and depends on the current. The pattern is formed during ~60 ns and each stratum's voltage settles at the constant level limited by arc discharges. We found that strata fractal dimension D=1.55±0.02 for all experiments, which means that the patterns are determined by a certain universal mechanism.

Degradation process of metallized film capacitors under high electrodynamic load was investigated. Pulse current overload factor exceeded 40. The polar effect of contact edges destruction was found. The average lifetime of different metallized film capacitors in pulse mode was evaluated. Dielectric frequency response testing during a capacitor's degradation was performed. Obtained spectra contain a loss peaks in a range of 1–100 kHz which move to lower frequencies region along with increasing of current pulse number. Possible reasons of such behavior are discussed.

The results of comparison of simultaneous partial discharge (PD) measurements by means of acoustic and electrical methods are presented. The difference between the single PD energies obtained by these methods was quantified. Since the acoustic method allows measuring only a part of the PD energy transmitted along the acoustic axis of the piezosensor, a method to evaluate a whole PD energy on the base of acoustic measurements is proposed. A point source acoustic wave distribution in dielectric medium was additionally investigated.

This paper presents the results of the experimental investigation and numerical simulation of electrodynamic destruction of metallized film capacitors electrodes during self-healing process. The degradation of intersegment gates of Al metallized patterned electrodes under high current load was studied. The numerical simulation was conducted by means of COMSOL Multiphysics software. The model takes into account the heat flow from metal layer to polymer film since it has significant influence on destruction process dynamics. The simulation results are in good agreement with the experimental data.

Metallized film capacitors have an ability to withstand the breakdown of dielectric film due to a “self-healing” feature. The optimal design of metallized electrodes' patterns guarantees high reliability of metallized film capacitors. This paper presents the results of numerical simulation of the intersegment gate current destruction during self-healing by means of COMSOL Multiphysics software. The model takes into consideration the heat flow from metal layer to polymer film since it has significant influence on destruction process dynamics. The simulation results were shown to be in good agreement with the experimental data.

Metallized film capacitors widely used in energy applications were studied. The experimental method for investigation of energy and dynamic characteristics of self-healing processes in real metal-film capacitors was developed. The commercial PET and PP MFCs of 0.22 – 1 μF capacitance and 63–250 V voltage were tested. Depending on applied voltage, 3 types of SH processes in MFC were discovered: single, repetitive, and multiple SH. Dependencies of self-healing energy on breakdown voltage were obtained. These dependencies are described by power law with the exponent n = 2.2–2.4 that significantly differs from literature data. The obtained data will be used for degradation and aging laws formulation for capacitors’ energy storage capability improvement.

Pulsed electrodynamic breakage of thin (∼20-nm-thick) aluminum films deposited onto polymer substrates have been experimentally studied. The character of film fracture depends on the level of supplied electric energy W. For 3.5 kJ/g < W < 4.3 kJ/g, discontinuities (striations) are formed in the transverse direction relative to the applied electric field. At high current densities on a level of ∼(1–3) × 1012 A/m2 and explosion times within 50–300 ns, the integral of action to explosion varies within (0.79–1.08) × 1017 A s/m2 depending on the rate of energy supply and differs from published data for relatively massive conductors.

Experimental studies of the dynamic characteristics of the self-healing processes in different metallized capacitor films are presented.

A theoretical modeling of the formation of Frenkel pairs and the diffusion of a self-interstitial atom in silicon crystals at normal and high (hydrostatic) pressures has been performed using quantum-chemical (NDDO-PM5), methods. It is shown that, in a silicon crystal, the most stable configuration of a self-interstitial atom in the neutral charge state (I 0 ) is the split configuration 〈110〉. The tetrahedral configuration is not stable, an interstitial atom being shifted from T position in a new position T 1 on a distance Δd = 0.2 A. The hexagonal configuration is not stable in NDDO approximation. The split 〈110〉 interstitial configuration remains the more stable configuration under hydrostatic pressure (P

Nanosecond microgap surface flashover in metalized capacitor polymer films at atmospheric air is investigated. The range of microgap is 10-1000 μm. Surface breakdown occurs between aluminum or zinc 10-20 nm thickness electrodes evaporated onto 10 μm polymer films (polypropylene, polyethylene terephthalate). The special method is used to obtain the gap size of 10-50 μm. For larger gaps the commercial capacitor segmented metallized film is used. The experimental voltage and current are measured using 2 GS/s digital oscilloscope and used for breakdown channel resistance calculation. Experimental data are analyzed on the base of known theoretical and empirical equations (Toepler, Rompe and Weizel, Vlastos, Goncharenko and others). It is shown that in the nanosecond time range Rompe and Weizel arc resistance equation is in the good agreement with experimental results.

Summary form only given. The exploding wire phenomenon is well researched for the micrometer-size conductors. Nevertheless the publications concerning exploding films of nanometer-thick are not so numerous. In this paper some experimental results of nanosecond exploding Al films vaporized on polypropylene substrates exposed to high-voltage pulses (up to 8 kV, 1 kA) are presented. The thickness of polypropylene film is 10 µm, sheet resistance of Al coating layer is 3 Ω/square (which corresponds to 20 nm of thickness). The maximum current density through the sample is 3*1012 A/m2. The dynamic and power characteristics are obtained for the explosion events. The optical registration of light emission during the explosion is also performed. Typical experimental current waveform comprised 3 phases: initial strike, dwell time and restrike, however at some conditions resrtrike may not occur. It was shown that dwell time is dependent on discharge voltage. Also some features of the process are found: the experimental specific action integral for exploding films is less than known one for exploding wires; complete Al film destruction energy density is several times less than a table Al evaporation energy density. The possible reasons of stated features are discussed.

A significant increase in the efficiency of modern metallized film capacitors has been achieved by the application of special segmented nanometer-thick electrodes. The proper design of the electrode segmentation guarantees the best efficiency of the capacitor's self-healing (SH) ability. Meanwhile, the reported theoretical and experimental results have not led to the commonly accepted model of the SH process, since the experimental SH dissipated energy value is several times higher than the calculated one. In this paper, we show that the difference is caused by the heat outflow into polymer film. Based on this, a mathematical model of the metallized electrode destruction is developed. These insights in turn are leading to a better understanding of the SH development. The adequacy of the model is confirmed by both the experiments and the numerical calculations. A procedure of optimal segmented electrode design is offered.