Fuchang Lin

Huazhong University of Science and Technology, Wuhan, Hubei, China

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Publications (60)39.28 Total impact

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    ABSTRACT: The breakdown and triggering characteristics of triggered vacuum switch (TVS) are very important features, and they affect the operation reliability of TVS. Both of them mainly depend on the electrode material, electrode shape, gap distance, and surface condition. For an optimized electrode's geometry, finite-element method electrostatic field simulations were conducted to evaluate the effect of geometric parameters on the electrostatic field strength and distribution. The distribution of electrostatic field of the TVS with multirod system (MTVS) is calculated by the finite method. The simulation results show that the geometric enhancement factor (GEF) is decreased with the increase of the fillet radius of the edge of the rod. In case of the fillet radius for the side face of rod 3 mm and the fillet radius of the top face of the rod is 5 mm, the GEF is decrease to a minimum value of 3. The breakdown voltage of MTVS was measured by the high-voltage direct current generator after switch currents with amplitude of 63 kA and width of 13 ms with the interval time of 10-15 min. The influences of electrode materials and operation times on the breakdown voltage and trigger characteristics are also studied. The experimental results show that the breakdown voltage of the optimized MTVS is higher than that of the non-optimized MTVS. The breakdown voltage of CuCr30 is higher than that of oxygen-free copper. In addition to, the trigger characteristics of MTVS are influenced mainly by the electrode materials, the fillet radius of electrode has a little effect on the triggering characteristics of MTVS.
    IEEE Transactions on Plasma Science 01/2014; 42(1):162-167. · 0.87 Impact Factor
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    ABSTRACT: Metallized biaxially oriented polypropylene film (BOPP) capacitors are widely used in pulsed power systems. When the capacitor is used as the energy storage equipment under high electric field, more charges should be provided to maintain the voltage of the capacitor. This should be ascribed to the completion of the slow polarization which may take several hours or even longer. This paper focuses on the stored charge in metallized BOPP film capacitors. The modeling of the stored charge by the equivalent conversion of circuits is conducted to analyse the slow polarization in the BOPP film. The 3-RC network is proposed to represent the time-dependent charge stored in the capacitor. A charging current measurement system is established to investigate the charge storage property of the capacitor. The measurement system can measure the long time charging current with a sampling rate of 300Hz. The total charge calculated by the charging current indicates that the stored charge in the capacitor under the electric field of 400 V∕μm is 13.5% larger than the product of the voltage and the capacitance measured by the AC bridge. The nonlinear effect of the electric field on the slow polarization charge is also demonstrated. And the simulation of charge storage based on the 3-RC network can match well with the trend of the stored charge increasing with the time.
    The Review of scientific instruments 10/2013; 84(10):104707. · 1.52 Impact Factor
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    ABSTRACT: A triggered vacuum switch (TVS) shows good performance when used in pulsed power systems. The time delay and lifetime are the important features of the TVS. We carry out several experiments to measure and analyze the time delay and lifetime characteristics of TVS with a multirod system. The results show that the time delay is strongly influenced by the polarity effect. The lifetime experiments are repeated for 1000 shots under two different operational modes. After repeated 1000-shot experiments, the TVSs are not damaged. The results prove that the TVS with a multirod system can work under a long lifetime in excess of 1000 shots. After the first 200 shots, the trigger voltage maintains between 40 and 1000 V, and the rise time and collapse time are around 2.5 μs.
    IEEE Transactions on Plasma Science 05/2013; 41(5):1307-1312. · 0.87 Impact Factor
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    ABSTRACT: Pulsed power supply (PPS) applied in the electromagnetic launch system must have a compact design and high reliability. In this paper, a PPS for electromagnetic launch system is built up. The main parts in a pulse forming unit (PFU) of a PPS are energy storage capacitors (8 kV/75 kJ), pulse-shaping inductor (10 μH), pulse thyristor, crowbar diode, and a Rogowski coil for current measuring. The energy storage density of the PFU is 0.74 MJ/m3. Eight PFUs form a pulse forming network (PFN) of 600 kJ. In many cases, the discharge current waveform of the PFN must be adjusted for lower peak value and lower electromagnetic force. On the basis of this PFN, in this paper, we analyze the effect of sequence discharge on the semiconductors. To prevent diode from overvoltage during the recovery process, different parameters of snubber circuit have been researched in the experiments. Finally, we set up a model of the serial augment rail gun in a personal simulation program with integrated circuit emphasis, and the safety of PFU can be affirmed by simulation if the voltage of the rail gun keeps positive during the course of the discharge.
    IEEE Transactions on Plasma Science 05/2013; 41(5):1300-1306. · 0.87 Impact Factor
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    ABSTRACT: 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.
    IEEE Transactions on Plasma Science 05/2013; 41(5):1313-1318. · 0.87 Impact Factor
  • Yi Liu, Xibo Feng, Fuchang Lin, Li Lee
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    ABSTRACT: Normally, a three-electrode spark-gap switch is controlled by the application of an external trigger impulse. In this paper, a novel self-breakdown sharpening switch based on the three-electrode spark-gap switch is proposed. However, in this paper, the trigger electrode is connected to ground through a resistor, with the prespark between the trigger and the main electrodes providing the electrons and ions that initiate conduction of the main gap. A prototype sharpening switch with a breakdown voltage of 116.0 kV ± 1.0 kV and a breakdown time of 3.396 μs ± 0.036 μs is described. When compared with a conventional two-electrode spark-gap sharpening switch, the novel sharpening switch has both a more stable breakdown voltage and lower jitter, and the dc breakdown and impulse breakdown characteristics of the two types of switches are presented and compared. When the impedance of the resistor connected to the trigger electrode is high, it is demonstrated that both the value of this resistor and also the type of load have little effect on the characteristics of the novel switch. However, the breakdown voltage of the novel sharpening switch was found to be sensitive to the rise time of the input pulse from the trigger generator. The prototype sharpening switch has a lifetime at least 20 000 shots and is now in use in a major pulsed power conditioning system.
    IEEE Transactions on Plasma Science 01/2013; 41(1):192-198. · 0.87 Impact Factor
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    ABSTRACT: The high energy density capacitors (HEDC) made of metallized polypropylene film possess characteristics of high reliability and is widely used in the pulsed power systems. In order to achieve a long life characteristic, the HEDC should be designed to age gracefully with a predictable lifetime. Thus there is an urgent demand in evaluating and predicting the lifetime of the HEDC. Lifetime evaluation of HEDC prototype in design is carried out by lifetime test of the HEDC element under relatively high electric field to reduce costs and shorten time. But experimental data show that the lifetime of HED prototype is far shorter than that of the element even under the same conditions. This paper firstly analyzes the different operational factors influencing lifetime performance based on Weibull distribution, such as the voltage, temperatures and so on. Empirically derived functions of lifetime scaling about operational factors are presented. Then lifetime relationship between the HEDC element and prototype is investigated by reliability analysis. At last, the lifetime prediction model is established with the consideration of operational factors and reliability.
    Pulsed Power Conference (PPC), 2013 19th IEEE; 01/2013
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    ABSTRACT: form only given. Metallized polypropylene film capacitor (MPPFC) is one of the key components in pulsed power system. In order to increase the reliability of the power source equipment, the lifetime of the capacitor must be extended. Self-healing is one of the main features of MPPFC. With the ongoing self healing, capacitance will reduce. If capacitance decreases to 5%, the capacitor is defined to life-ending. Many tests have demonstrated that lifetime performance of capacitor is closely related to some operational factors such as electric field, temperature, and pulse repetition rate and so on. But the effect of pulse discharge current on lifetime has not been thoroughly studied. The aim of this paper is to study the pulse discharge current performance of MPPFC. End connection peak current density (Id) and current reversal coefficient (β) are two critical parameters affecting the lifetime of the MPPFC. Experiments are designed to study the lifetime performance under different Id and β. The results show that the lifetime of capacitor is extremely sensitive to β and less sensitive to Id if the Id is less than a certain value. The results also reveal a kind of sudden capacitance drop phenomenon, which indicates that the probability of the sudden capacitance drop increases with the Id. And as the conclusion, the paper gives empirically derived life-scaling equations of Id and β.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: When the Metallized polypropylene film capacitors (MPPFCs) are used under a high electric field, an obvious voltage decay phenomena will occur. And the voltage decay may finally decrease the practical output energy of the capacitor. This kind of phenomena is not only due to the influence of the dielectric conduction, but also the slow polarization of the dielectric. Due to defects or amorphous regions in the dielectric material, there is slow polarization in MPPFC when it is applied under high electric field. The completion of slow polarization may take several seconds or several minutes or even longer. If MPPFC is disconnected from the power source without fully charged (the slow polarization process is unfinished), the voltage decay will occur in a relatively significant value for the slow polarization and dielectric conduction.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: In high energy density capacitors, the electrical conduction in the dielectric may result in the leakage and the reduction of the energy efficiency. This paper investigates the electrical conduction mechanism of metallized biaxially oriented polypropylene (BOPP) film based on a revised Poole–Frenkel (PF) effect and field-enhanced carrier mobility. The field-enhanced carrier mobility which is not taken into account in traditional PF effect is investigated in the revised PF effect based on the carrier hopping mechanism. Moreover, the coefficient of the PF effect (βPF) which stands for the variation of the barrier height is discussed. Experiments are performed to measure the electrical conductivity of the BOPP film under different electric fields. Influencing factors such as metallized electrodes, the interlayer pressure in the winding, and the crystallinity may decrease the conductivity. With a fitted jump distance of 0.6 nm, the calculated conductivities based on the revised PF effect do match well with experimental results.
    Journal of Electrostatics 01/2013; 71(6):958–962. · 1.00 Impact Factor
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    ABSTRACT: In pulsed power systems, metallized polypropylene film capacitors (MPPFCs) facilitate the operation of the polypropylene film with a relatively small margin to its dc breakdown strength. The insulation resistance (IR) is one of the important factors that result in the reduction of the energy efficiency, as it represents a current leakage path through the dielectric. This paper concentrates on the leakage phenomenon in MPPFCs by the measurement and analysis of IR. Measurement of the IR under high electric fields is feasible due to the self-healing capability and a measuring system is established to measure IR under various electric fields. To sufficiently investigate IR changing with the electric fields, IR under low electric fields are also investigated. The results indicate that the time constant (called Equivalent IR) is extremely sensitive to the electric field and IR changes little under electric field lower than 10 V/μm. The assumption that influence of surface leakage in the margin on IR could be neglected is also validated by experiments. Finally, theoretical calculation of Equivalent IR based on the Poole-Frenkel (PF) effect is carried out.
    IEEE Transactions on Dielectrics and Electrical Insulation 01/2013; 20(4):1315-1320. · 1.36 Impact Factor
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    ABSTRACT: This article devotes itself to a compact pulse forming network (PFN) of 16MJ for rail gun. The PFN is composed of 156 pulse forming units (PFU), and each unit stores 103kJ energy. The main components of PFU are energy storage capacitor, pulse-shaping inductor, pulse thyristor, crowbar diode and Rogowski coil for current-measuring. The rated voltage of PFU is 10.8kV. Metallized PP film is used as dielectric material of the pulsed capacitors, whose energy density is 1.5 kJ/L and whose life time is above 2000 shots. The pulse thyristor with a wafer diameter of 4 inches can endure the pulse current of 150kA. For convenience of integral assembling, the crowbar diodes also adopt 4 inches wafers. The trigger device of thyristor takes the energy from the main pulse capacitor of 103kJ, so the common insulating transformer can be abandoned. This mode decreases the volume and weight of the trigger unit greatly. Single PFU produces the pulse current of 120kA, and its energy storage density is 0.88MJ/m3. The trigger time of every unit in the 16MJ PFN can be adjusted flexibly for the different shape of the total current. All PFUs discharge at the same time with the load of rail gun so that they can produce the spire current of 3-4MA. And they can be triggered at some special interval in order to achieve the quasi-flat wave, which benefits the manufacture of the rail and the armature. In a whole, the PPS consists of PFN, charging power supply, control system and current junction station. Its configuration is so compact that all components can be placed in 2 big frames. Every frame with size of 7.5m*2.2m*2.3m is suitable to be transported in a container.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: Metallized polypropylene film capacitors (MPPFCs) possess characteristics of high reliabilities and high energy densities, so they are widely used in the pulse power systems. MPPFC prototypes with high voltage and large capacitance are composed of a number of cylindrical MPPFC elements connecting in series or in parallel. The experimental data show that the lifetime of MPPFC prototypes is far shorter than that of MPPFC elements under the same voltage stress. This paper analyses operational factors that affect influence the lifetime of MPPFCs, and predicts the lifetime under various operational factors based on the experimental results. The relationship between MPPFC elements and MPPFC prototypes in terms of lifetime is presented with a reliability analysis of the Weibull distribution, and is validated through experiments. Finally this paper presents a lifetime prediction model. The results suggest that the predicted data could match well with experimental results. This paper is devoted more to the lifetime analysis under various operational factors and less to theoretical physical analysis.
    Microelectronics Reliability 01/2013; 53(12):1962–1967. · 1.14 Impact Factor
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    ABSTRACT: 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.
    IEEE Transactions on Plasma Science 01/2013; 41(10):3063-3068. · 0.87 Impact Factor
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    ABSTRACT: Repetitive pulsed power technology has been developed fast during these decades, while a small-size, compact, portable, and reliable repetitive pulsed power source has a very extensive application prospect in defense, industry, and laboratory research fields. In this paper, a compact repetitive pulsed power source based on Tesla transformer with build-in coaxial pulse forming line has been developed. The design, construction and experiment testing are presented in detail. In order to get high a couple coefficient and turns ratio, open-loop magnetic core and conic secondary turns are adopted, respectively. The maximum charging voltage of the transformer is 240 kV with transformer oil insulation while the primary circuit comprises a fast thyristor as the low-voltage switch. The weight of the device with the small-size (20×20×70mm3) is less than 30 kg. Using a gas switch without blowing, the device is capable of delivering, to a 100 ohm load, an output pulse of 150 kV in peak voltage with a rise time of 2 ns and a pulse length of 7 ns, at the repetition rate of 50Hz.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: form only given. Two-electrode Graphite Spark Gap Switch (TGSGS) is used as the main discharge switch in Pulsed Power Conditioning System (PPCS). Normally the TGSGS is controlled by the application of an external trigger impulse. The trigger impulse with peak value of more than 120 kV and rise time of less than 30 ns is provided by a trigger generator based on pulse transformer1. In this paper, the operating situation of the TGSGS and the injection of the trigger generator are investigated and described. When the main capacitor is charged on different DC voltages, the breakdown voltages of the TGSGS under the trigger impulse are measured. The calculation and the experimental results of the breakdown voltage under ns impulse are presented and compared. The results indicate that the over-voltage breakdown of the TGSGS in PPCS is sensitive to the peak value, and rise time of the trigger impulse, and does not require too much energy. At last the time delay and jitter of the TGSGS in PPCS is presented.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: form only given. Two-electrode Graphite Spark Gap Switch (TGSGS) is used as the main discharge switch in Pulsed Power Conditioning System (PPCS). Normally the TGSGS is controlled by the application of an external trigger impulse. The trigger impulse with peak value of more than 120 kV and rise time of less than 30 ns is provided by a trigger generator based on pulse transformer1. In this paper, the operating situation of the TGSGS and the injection of the trigger generator are investigated and described. When the main capacitor is charged on different DC voltages, the breakdown voltages of the TGSGS under the trigger impulse are measured. The calculation and the experimental results of the breakdown voltage under ns impulse are presented and compared. The results indicate that the over-voltage breakdown of the TGSGS in PPCS is sensitive to the peak value, and rise time of the trigger impulse, and does not require too much energy. At last the time delay and jitter of the TGSGS in PPCS is presented.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: Analysis of breakdown mechanism in gas-insulated trigatron switches is important for the engineering design and function prediction. Based on the gas discharge theory, a physical model was proposed to estimate the breakdown time for gas-insulated trigatron switches. And the model can explain the breakdown in the trigatron switches with two modes of the breakdown mechanism, i.e., fast breakdown mode (FBM) and slow-breakdown mode (SBM). Based on Raether breakdown criterion, this paper discussed the factors affecting on the E-field enhancement. The E-field is composed of the static E-field and the dynamic E-field, which leads to transformation of breakdown mechanism. Some coefficients could be determined by experiment and simulation, which are helpful to get the quantitative solution of breakdown time.
    IEEE Transactions on Dielectrics and Electrical Insulation 01/2013; 20(4):1069-1075. · 1.36 Impact Factor
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    ABSTRACT: Working characteristics of a three-electrode trigatron spark gap is discussed in this paper. Breakdown probability is proven to fit a Weibull distribution. For an engineering application, the lower limit of undervoltage ratio depends on breakdown probability, and the upper limit of undervoltage ratio depends on self-breakdown probability. Some characteristics have been determined experimentally, such as the influence of the air pressure and the influence of the undervoltage ratio on spark gap operation. Curve fitting and quasi-data mining are good methods for research on triggering characteristic in the paper. Therefore, a maximum operation range curve and a boundary line of expected delay time could be determined by application requirements, theory calculation, experimental data and curve fitting. On this basis, optimization operation range could be obtained, which represents a preferable performance of breakdown with expected delay time. It may provide guidance for engineering application.
    IEEE Transactions on Dielectrics and Electrical Insulation 01/2013; 20(4):1032-1039. · 1.36 Impact Factor
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    ABSTRACT: In a high-powered single pulse system, the graphite electrode is better than other common metal electrodes for high energy transfer and pulse discharge. In this paper, the erosion mechanism of graphite electrode is investigated with the thermodynamics theory and the experimental results. Based on a simplified mathematical model, the graphite electrode erosion process of high-powered spark gap switch is also analyzed. The analysis results show that the relationship of the graphite electrode erosion and the charge transfer is linear, which is accordant with the experimental results.
    The Review of scientific instruments 01/2012; 83(1):013504. · 1.52 Impact Factor