Metallized Film Capacitors Research Articles

Study on Charging Characteristics and Voltage Maintaining Characteristics of Metallized Film Capacitors

High energy density capacitor is a key device in pulse power system such as Electromagnetic Gun system and Laser Fusion system. The increase of energy density of capacitor is beneficial from emerge of metallized technology in electrode and advancement in manufacturing. In this paper, first, the influences of different temperature, electric field strength and Ω/square on the insulation resistance and voltage drop are compared for proper use of capacitor and for manufacture improvement purpose. Then, influences of different charging rate and temperature on capacitor are compared for selecting a reasonable charging method. A capacitor is united by several metallized capacitors with series or parallel connection. The arrangement method and the difference of circumstance result in the temperature difference among the capacitors and influence the characteristics of capacitor. The test with two series capacitor be charged under different temperature indicates that the difference of temperature results in the difference of the voltage distribution. The difference is greater as the temperature increase. The results of the test also show that the time of charge is an important factor which influences the voltage of the capacitor obviously.

T pattern fuse construction in segment metallized film capacitors based on self-healing characteristics

The breakdown happens in metallized polypropylene film (MPPF) capacitor can be classified into two cases: the first one is self-healing, which means that the insulation will recover after the breakdown; the other one is self-healing failure, which means that the capacitor will fail because of short-circuit fault. In this paper, the MPPF capacitor applied in DC filtering which adopt the T pattern segment film technology is investigated. To simulate the two cases mentioned above, a model based on self-healing experiment data is built by Power Systems Computer Aided Design (PSCAD). The current density flowing through the fuse and fuse energy is calculated and analyzed. Meanwhile, the fuse burn-out criteria are investigated according to electrical explosion theory and phase transition energy of segment metallized film fuse. The fuse design methodology of T pattern segment film is presented and a design case is provided.

Numerical characterization of local electrical breakdown in sub-micrometer metallized film capacitors

In metallized film capacitors, there exists an air gap of about 0.2 μm between the films, with a pressure ranging generally from 1–30 atm. Because of the created potential difference between the two films, a microdischarge is formed in this gap. In this paper, we use an implicit particle-in-cell Monte Carlo collision simulation method to study the discharge properties in this direct-current microdischarge with 0.2 μm gap in a range of different voltages and pressures. The discharge process is significantly different from a conventional high pressure discharge. Indeed, the high electric field due to the small gap sustains the discharge by field emission. At low applied voltage (∼15 V), only the electrons are generated by field emission, while both electrons and ions are generated as a stable glow discharge at medium applied voltage (∼50 V). At still higher applied voltage (∼100 V), the number of electrons and ions rapidly multiplies, the electric field reverses, and the discharge changes from a glow to an arc regime.

Electric Field and Temperature Dependence of Electrical Conductivity in Biaxially Oriented Polypropylene Films

In pulsed power systems, metallized film capacitors facilitate the operation of the film with a relatively small margin to its dc breakdown strength. Electrical conduction in metallized biaxially oriented polypropylene (BOPP) film may result in the leakage in high energy density capacitors and thus the reduction of the energy efficiency. This paper investigates the mechanism of the electric field and temperature dependence of electrical conduction in the BOPP film capacitor. A proposed model for the electrical conductivity takes into consideration both the Poole-Frenkel effect and field-enhanced carrier mobility. Experiments are performed to measure the electrical conductivity of the BOPP film at different electric fields and temperatures.

Operation of a 2.4-MJ Pulsed Power System for Railgun

A 2.4-MJ capacitive pulsed power system (PPS) for a railgun was fabricated, installed, and tested. It consists of four independent 600-kJ segments. Each segment contains six 100-kJ capacitor bank modules, a capacitor charger, a circuit for charge and dump, a relay box, and a segment controller. The 100-kJ unit module is composed of a metalized film capacitor, semiconductor switches, and an inductor. It was designed for a safe operation within 10 kV and 75 kA. All the modules in a segment are charged with the same voltage, but the trigger times of each module are individually controllable. With the 2.4-MJ PPS and a medium caliber railgun, discharge experiments in the breech-shorted condition and launch experiments using aluminum armatures were conducted. With the results, we modified the electrical circuit parameters of the PPS from the initial designed values. The circuit simulation using the modified parameters showed good agreement with the experiment data.

Parameter learning for the belief rule base system in the residual life probability prediction of metalized film capacitor

The Inertial Confinement Fusion (ICF) laser device consists of thousands of Metalized Film Capacitors (MFC). The Belief Rule Base (BRB) system has shown privileges in reflecting complex system dynamics. However, the BRB system requires the referenced values of each attribute to be limited. The traditional BRB learning and training approaches are no longer applicable since the referenced values of the attributes in the BRB system are pre-determined. A parameter learning approach is proposed with three strategies and each strategy is designed for one specific scenario. Strategy I (for Scenario I) is designed when only the training dataset is selectable. Strategy II (for Scenario II) is designed when new referenced values are predictable yet there is only one scale in the conclusion part. Strategy III (for Scenario III) is designed when new referenced values are predictable and there are multiple scales in the conclusion part. The Differential Evolution (DE) algorithm is used as the optimization engine to identify the key referenced values. A case is studied to validate the efficiency of the proposed parameter learning approach with multiple referenced values. The comparative results show that the parameter learning approach performs best in Scenario III.

Eliminating infant mortality in metallized film capacitors by defect detection

A PoF approach to mitigating infant mortality is proposed which includes (1) conducting reliability capability and product maturity analyses; (2) identifying defects through non-destructive analysis, if possible; and (3) developing electrical tests to screen out early failures. The non-destructive analysis approach was outlined using die attach in a power module as a test bed, while the electrical testing approach was outlined using film capacitors. More data is being gathered to validate that the electrical test provides an early differentiation of change in capacitance over time between good and defective capacitors.

Metallized polymer film capacitors ageing law based on capacitance degradation

Passive components, particularly capacitors, are very used devices in power electronics applications providing key function on board. Nevertheless, capacitors breakdowns can have catastrophic consequences on the financial and human scale; a good acquaintance of their deterioration over time would contribute in the improvement of the availability of the whole system by performing a predictive maintenance on the component. This operation requires the knowledge of the capacitor ageing law and their failure mechanisms associated to the application. Capacitance loss can be mainly attributed to the self-healing process occurring in metallized film capacitors when used under high steady electrical and thermal stresses. In this paper, a capacitance ageing law is proposed based on the identification of voltage and temperature degradation kinetics from three experimental floating ageing tests performed at different voltage and temperature constraints. A total of 34 capacitors provided from different manufacturers using polyester film as dielectric have been studied and compared to validate the proposed law.

Capacitive energy storage and recovery for synchrotron magnets.

Feasibility studies on capacitive energy storage and recovery in the main-ring synchrotron of the Japan Proton Accelerator Research Complex were conducted by circuit simulation. The estimated load fluctuation was 96 MVA in total for dipole magnets, which is likely to induce a serious disturbance in the main grid. It was found that the energy stored in the magnets after the excitation period can be recovered to the storage capacitor by controlling the voltage across the energy-storage capacitor using a pulse-width-modulation converter and reused in the next operational cycle. It was also found that the power fluctuation in the main grid can be reduced to 12 MVA. An experimental evaluation of an aluminum metalized film capacitor revealed that capacitance loss was induced by a fluctuating voltage applied to the storage capacitor when applying the proposed method. The capacitance loss was induced by corona discharge around the edges of segmented electrodes of a self-healing capacitor. The use of aluminum-zinc alloy was evaluated as a countermeasure to mitigate the effect induced by the corona discharge. For a zinc content of 8%, which was optimized experimentally, a capacitor with a sufficient life time expectancy of 20 years and a working potential gradient of 250 V/μm was developed.

Improved model of metalized film capacitors

Metalized film capacitors are commonly used components in power electronics applications and their characteristics are drastically dependent on their operating frequency. Parasitic parameters could appear at low and high frequencies and disturb substantially the behavior of the component. Proper design of metalized film capacitors requires an understanding of all parasitic parameters' sources and their impacts on the circuit operation. This paper presents a modeling approach based on the complex form of the capacitor impedance to build its equivalent electrical circuit. This approach proved to be more accurate than the traditional modeling technique of identifying the electrical parameters using the modulus of the component impedance. Two different types of capacitors were tested; experimental results allowed to validate our model from 10 kHz to 35 MHz.

通过电容器层间压强的增强提高电容器寿命

通过电容器层间压强的增强提高电容器寿命

Lifetime Improvement of Metallized Film Capacitors by Inner Pressure Strengthening

Metallized polypropylene film capacitors (MPPFCs) are widely used in pulse power systems for their characteristics of high reliabilities, high energy densities, and excellent pulse power handling capabilities. The teardown showed that the capacitance loss decreased gradually from the outer layers to the inner layers in a cylindrical MPPFC winding. This paper concentrates on the inner pressure in the MPPFC winding. First, the effects of the inner pressure on the self-healing and the lifetime are investigated. The lifetime can be extended by the inner pressure strengthening. Second, an inner pressure calculation formula is presented. The effects of the heat treatment and wrapped film on the pressure are considered. In addition, the heat treatment and wrapped films are chosen to strengthen the pressure. Finally, the experiments are designed to validate the effect of the lifetime improvement by the methods of the inner pressure strengthening. Results show that the lifetime can be extended by 30% with rational heat treatment and by 38% with rational design of the wrapped film.

Lifetime Prediction of Metallized Film Capacitors Based on Capacitance Loss

Metallized film capacitors possess characteristics of self-healing, high reliability, and long lifetime. Lifetime and reliability of capacitors are the key factors that ensure the stability of the electromagnetic launch system. In the capacitor lifetime test, it is a time-consuming work to get enough capacitance loss (CL) data to characterize the performance of the capacitor. Thus, it is necessary to analyze experimental data by effective lifetime prediction model (LPM). This paper first introduces the characteristics of CL in lifetime test. Then, it introduces traditional LPMs such as least square method (LSM) and Weibull distribution model (WDM). LSM is only appropriate when CL is uniform and steady, and it cannot analyze the lifetime reliability. WDM works best when large quantities of lifetime experiment data are acquired. In this paper, some new LPMs such as Birnbaum-Saunders distribution model and Poisson distribution model are introduced. New LPMs fully use CL in each shot, and it could faithfully reflect the work conditions of the capacitor. The analysis methods and steps of each model are put forward. In order to fully introduce these models, lifetime calculations are carried out based on the aforementioned LPMs.

Investigation of performance degradation in metallized film capacitors

Zn–Al metallized film capacitors in two different production stages were investigated to explain the decrease of capacitors performance with time. Unsealed and sealed capacitors with different aluminium content in metallization layer were investigated. Scanning electron microscopy (SEM) was used to image the surface of the metallization layers, energy dispersive X-ray spectroscopy (EDS) was used to determine the chemical composition and Auger electron spectroscopy (AES) was used to determine the chemical composition of the top of the metallization layers as well as to estimate the degree of oxidation. It was found that air humidity degraded the metallization layer of unsealed capacitors, especially at lower Al contents. Sealed capacitors were exposed to high electric fields, typical for standard usage. It was found – rather unexpectedly – that the performance was decreased by increasing Al content. A crystallographic explanation was proposed.

Metallized Film Power Capacitors End-of-Life Study Through Monitored Destruction Tests

A wide range of experiments was performed on metallized film capacitors. The monitoring of destruction tests was used to analyze the electrical properties of artificial critical defects. It is shown herein that these defects in the windings of the capacitors have a wide range of electrical properties and the behavior of the capacitor in the test is strongly related to these properties. A model is proposed to describe the degeneration of dielectric failure, the use of this model can help to predict the behavior of capacitors when they reach the end of life and to a more accurate design of the protection systems.

A Dual-Capacitors Type Energy Recovery Power System for Repetitive Pulsed High Magnetic Fields

As a flexible and convenient tool, a repetitive pulsed high magnetic field (RPHMF) would be employed for scientific research and industrial applications. A novel RPHMF system design adopting a dual-capacitors type energy recovery power system is introduced in this paper. The energy stored in the magnet can be fed back to the capacitor by a choke coil and a resonant capacitor while the energy dissipated in the discharge will be replenished to the capacitor through a high frequency resonant capacitor charging power system (CCPS). The main advantages of the design are as followed: first, the energy feedback make the system more efficient; second, during the whole process there is no reverse voltage on the metalized film capacitors, improving the energy storage capacitors’ service lifetime and reliability remarkably; finally, convenience can be brought to the high frequency CCPS’s application. In this paper, theoretic analysis of RPHMF system is described and an experimental device with a bitter magnet as the load is built to test the design for its verification. A 1.2 Hz, 8 T repetitive pulsed high magnetic field is generated. Experimental results show that there is no reverse voltage on the energy storage capacitors in the whole process. The factors influencing the efficiency and frequency of the system are analyzed in detail.

ENHANCING PERFORMANCE OF HIGH VOLTAGE METALLIZED FILM CAPACITORS BY USING NEW INDUSTRIAL NANO-COMPOSITES

This paper explains the enhancement on the performance of conventional High voltage metalized film capacitor doped with the Nanoparticles; the studied model has been discussed how the characteristics of High voltage metalized film capacitor has been enhanced depending on the concentration of the doped Nanoparticles and also their electric and dielectric properties. Also, this research investigates novel Nano-metric industrial materials for enhancing the electrical performance of multi section metalized film capacitors which satisfy a large variety of ac applications, electronic applications, and optimizing the characteristics of metalized film capacitors for specific applications by selecting suitable nanocomposite materials. Adding nanofillers to the conventional materials of multi section metalized film capacitors has enhanced the dielectric constant, dielectric strength, self-healing properties, temperature stability and volumetric efficiency that allowing achieving the highest capacitance per unit volume for this type of capacitors. Theoretical results have been investigated for comparing with conventional structure materials and new nanocomposite industrial materials of multi section metalized film capacitor. Finally, the present contribution has computed equivalent series inductance (ESI), equivalent series resistance (ESR), volumetric energy density, peak discharge current …etc. for multi section, high voltage windings, including limitations caused by various new nanocomposite materials.

Reliability Assessment of Metallized Film Capacitors using Reduced Degradation Test Sample

Metallized film capacitor is a type of product with a long lifetime and high reliability. It is difficult to assess the lifetime and reliability using the traditional statistical inference method which is based on the large number of testing data. This paper presents a new testing methodology, called T‐performance degradation test, by dividing the test process into several stages. In each stage, the sample size of working capacitors under test decreases stage by stage until the test lasts enough time with few survival capacitors. Leveraging the T‐performance degradation data, this paper further presents a reliability assessment model to predict the lifetime of the high‐performance capacitors. Finally, the reliability assessment model is demonstrated on a type of high‐performance metallized film capacitors used in the energy module of the laser facility. Copyright © 2012 John Wiley & Sons, Ltd.

高场强下金属化膜电容器绝缘电阻特性

高场强下金属化膜电容器绝缘电阻特性

500 kV全固态Marx发生器

The paper presents a 500 kV all-solid-state Marx generator adopting Z type circuit. In this Marx generator, twenty-eight isolated gate bipolar transistors(IGBTs) serial modules were utilized as controllable switches. The maximum working voltage of each IGBTs module was designed as high as 22 kV, and the repetition rate at full load condition was designed as high as 200 Hz. The ladder type pulse-forming-networks (PFNs) consisting of metallized film capacitors and wound inductors were designed as energy storage and pulse-forming components. Experimental results indicate that the Marx generator can run with 500 kV output pulses and 50 Hz repetition rate in burst-mode successfully. The peak output pulse voltage of this generator is approximately the same as that of the highest power solid-state Marx generator ever reported, while the peak current is almost twice, reaching 1 000 A. The maximum pulsed power of the generator is as high as 500 MW. As the capacitors were utilized as energy storage components, the pulse width can be adjusted from 3 s to 10 s continuously.