In response to the problem of frequent leakage and false alarm of partial discharge insulation defects in GIS,this paper conducts experimental research on intermittent discharge characteristics of common solid insulat...In response to the problem of frequent leakage and false alarm of partial discharge insulation defects in GIS,this paper conducts experimental research on intermittent discharge characteristics of common solid insulation defects in GIS.Using true GIS to build amulti-source testing platform for intermittent discharge of solid insulation defects,and using pulse current method,ultra-high frequency method,ultrasonic method,and gas characteristic component detectionmethod to study the variation law of intermittent discharge characteristics of solid insulation defects.The results showthat:the intermittent discharge state of metal fouling defects on the solid insulation surface decreases with the extension of the discharge time,the discharge time interval as a whole shows an increasing trend,and the metal fouling defects on the solid insulation surface in the intermittent discharge state is difficult to develop into a breakdown discharge fault.The overall discharge amount of air gap defects inside solid insulation also shows the law of increasing first and then decreasing,and the discharge amount of air gap defects inside solid insulation stays at a large level for a long time during intermittent discharge,and there is a risk of breakdown,and the discharge will gradually evolve into continuous discharge;ultrasonic method and characteristic component detection method cannot realize the effective perception of intermittent discharge of metal fouling.The 50-period mapping information commonly used in the power field cannot reflect the intermittent discharge variation law of solid insulation,and the 200-period UHF mapping composed of four groups of 50-period UHF mapping data can initially derive the intermittent discharge distribution law of solid insulation defects.The research results of this paper are of great significance to expand the knowledge of intermittent discharge characteristics and the detection of GIS discharge defects in the field.展开更多
A novel lateral insulated gate bipolar transistor on a silicon-on-insulator substrate SOI-LIGBT with a special low-doped P-well structure is proposed.The P-well structure is added to attach the P-body under the channe...A novel lateral insulated gate bipolar transistor on a silicon-on-insulator substrate SOI-LIGBT with a special low-doped P-well structure is proposed.The P-well structure is added to attach the P-body under the channel so as to reduce the linear anode current degradation without additional process.The influence of the length and depth of the P-well on the hot-carrier HC reliability of the SOI-LIGBT is studied.With the increase in the length of the P-well the perpendicular electric field peak and the impact ionization peak diminish resulting in the reduction of the hot-carrier degradation. In addition the impact ionization will be weakened with the increase in the depth of the P-well which also makes the hot-carrier degradation decrease.Considering the effect of the low-doped P-well and the process windows the length and depth of the P-well are both chosen as 2 μm.展开更多
An X-band magnetically insulated transmission line oscillator （MILO） is designed and investigated numerically and experimentally for the first time. The X-band MILO is optimized in detail with KARAT code. In simulat...An X-band magnetically insulated transmission line oscillator （MILO） is designed and investigated numerically and experimentally for the first time. The X-band MILO is optimized in detail with KARAT code. In simulation, the X-band MILO, driven by a 720 kV, 53 kA electron beam, comes to a nonlinear steady state in 4.0 ns. High-power microwaves （HPM） of TEM mode is generated with an average power of 4.1 GW, a frequency of 9.3 GHz, and power conversion efficiency of 10.870 in durations of 0-40 ns. The device is fabricated according to the simulation results. In experiments, when the voltage is 400 kV and the current is 50 kA, the radiated microwave power reaches about 110 MW and the dominating frequency is 9.7GHz. Because the surfaces of the cathode end and the beam dump are destroyed, the diode voltage cannot increase continuously. However, when the diode voltage is 400 kV, the average power output is obtained to be 700 MW in simulation. The impedance of the device is clearly smaller than the simulation prediction. Moreover, the duration of the microwave pulse is obviously shorter than that of the current pulse. The experimental results are greatly different from the simulation predictions. The preliminary analyses show that the generations of the anode plasma, the cathode flare and the anode flare are the essential cause for the remarkable deviation of the experimental results from the simulation predictions.展开更多
It has been proved that the thermally insulated ocean pipeline has advantages over the conventional pipe-in-pipe pipeline. The risk of using the thermally insulated pipeline is that the exterior layers covering the st...It has been proved that the thermally insulated ocean pipeline has advantages over the conventional pipe-in-pipe pipeline. The risk of using the thermally insulated pipeline is that the exterior layers covering the steel pipe may be. pulled off if the shear stress on the interface induced by the pullout fore from the tensioner is greater than the binding fore between two neighboring layers during installation. This paper develops a procedure to calculate the shear stress on the interface. The binding force between two neighboring layers can be determined with full scale model tests. The safety of the thermally insulated pipe under installation can then be checked by comparison of the interface shear stress with the binding force.展开更多
A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/...A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL.展开更多
Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this ...Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this paper, which is one of the most basic ways for diagnosis of insulation condition. Methods Ultra high frequency(UHF) PD detection method by using internal sensors has been proved efficient, because it may avoid the disturbance of corona, but the sensor installation of this method will be limited by the structure and operation condition of GIS. There are some of electromagnetic (E-M) waves leak from the place of insulation spacer, therefore, the external sensors UHF measuring PD technique is applied, which isn't limited by the operation condition of GIS. Results This paper analyzes propagated electromagnetic (E-M) waves of partial discharge pulse excited by using the finite-difference time-domain (FDTD) method. The signal collected at the outer point is more complex than that of the inner point, and the signals' amplitude of outer is about half of the inner, because it propagates through spacer and insulation slot. Set up UHF PD measuring system. The typical PD in 252kV GIS bus bar was measured using PD detection UHF technique with external sensors. Finally, compare the results of UHF measuring technique using external sensors with the results of FDTD method simulation and the traditional IEC60270 method detection. Conclusion The results of experiment shows that the UHF technique can realize the diagnosis of insulation condition, the results of FDTD method simulation and the result UHF method detection can demonstrate each other, which gives references to further researches and application for UHF PD measuring technique.展开更多
In this paper, a novel dual-gate and dielectric-inserted lateral trench insulated gate bipolar transistor （DGDI LTIGBT） structure, which features a double extended trench gate and a dielectric inserted in the drift ...In this paper, a novel dual-gate and dielectric-inserted lateral trench insulated gate bipolar transistor （DGDI LTIGBT） structure, which features a double extended trench gate and a dielectric inserted in the drift region, is proposed and discussed. The device can not only decrease the specific on-resistance Ron,sp , but also simultaneously improve the temperature performance. Simulation results show that the proposed LTIGBT achieves an ultra-low on-state voltage drop of 1.31 V at 700 A·cm-2 with a small half-cell pitch of 10.5 μm, a specific on-resistance R on,sp of 187 mΩ·mm2, and a high breakdown voltage of 250 V. The on-state voltage drop of the DGDI LTIGBT is 18% less than that of the DI LTIGBT and 30.3% less than that of the conventional LTIGBT. The proposed LTIGBT exhibits a good positive temperature coefficient for safety paralleling to handling larger currents and enhances the short-circuit capability while maintaining a low self-heating effect. Furthermore, it also shows a better tradeoff between the specific on-resistance and the turnoff loss, although it has a longer turnoff delay time.展开更多
The intersection point of the characteristic magnetic field line（CMFL） crossing the anode boundary with the discharge channel wall, and its influence on thruster performance and the energy and flux of ions bombardin...The intersection point of the characteristic magnetic field line（CMFL） crossing the anode boundary with the discharge channel wall, and its influence on thruster performance and the energy and flux of ions bombarding the channel wall, have been studied numerically. The simulation results demonstrate that with the increase in distance from the crossover point of the CMFL with the channel wall to the bottom of the thruster channel, the ionization rate in the discharge channel gradually increases; meanwhile, the ion energy and ion current density bombarding the channel wall decreases. When the point of the CMFL with the channel wall is at the channel outlet, the thrust, specific impulse, and efficiency are at a maximum, while the ion energy and ion current density bombarding the channel wall are at a minimum. Therefore, to improve the performance and lifetime of the thruster, it is important to control the point of intersection of the CMFL with the channel wall.展开更多
This paper introduces the Insulated gate bipolar transistor(IGBT)in- verter for arc welding.The principle of the inverter,the structure and charac- teristics of IGBT and the current feedback system using LEM current t...This paper introduces the Insulated gate bipolar transistor(IGBT)in- verter for arc welding.The principle of the inverter,the structure and charac- teristics of IGBT and the current feedback system using LEM current transduc- er are discussed.By the measurement of its efficiency and power factor and the tests of welding processes,the developed 150A IGBT inverter proves to be a kind of energy-saving portable power supply for arc welding with broad prospects.展开更多
A high voltage（〉 600 V） integrable silicon-on-insulator（SOI） trench-type lateral insulated gate bipolar transistor（LIGBT） with a reduced cell-pitch is proposed.The LIGBT features multiple trenches（MTs）：two o...A high voltage（〉 600 V） integrable silicon-on-insulator（SOI） trench-type lateral insulated gate bipolar transistor（LIGBT） with a reduced cell-pitch is proposed.The LIGBT features multiple trenches（MTs）：two oxide trenches in the drift region and a trench gate extended to the buried oxide（BOX）.Firstly,the oxide trenches enhance electric field strength because of the lower permittivity of oxide than that of Si.Secondly,oxide trenches bring in multi-directional depletion,leading to a reshaped electric field distribution and an enhanced reduced-surface electric-field（RESURF） effect.Both increase the breakdown voltage（BV）.Thirdly,oxide trenches fold the drift region around the oxide trenches,leading to a reduced cell-pitch.Finally,the oxide trenches enhance the conductivity modulation,resulting in a high electron/hole concentration in the drift region as well as a low forward voltage drop（Von）.The oxide trenches cause a low anode-cathode capacitance,which increases the switching speed and reduces the turn-off energy loss（Eoff）.The MT SOI LIGBT exhibits a BV of 603 V at a small cell-pitch of 24 μm,a Von of 1.03 V at 100 A/cm-2,a turn-off time of 250 ns and Eoff of 4.1×10？3 mJ.The trench gate extended to BOX synchronously acts as dielectric isolation between high voltage LIGBT and low voltage circuits,simplifying the fabrication processes.展开更多
This paper puts forward a novel magnetically insulated transmission line oscillator （MILO） for the first time which takes a modified HEM11 mode as its main interaction mode. The excitation of the oscillation mode is...This paper puts forward a novel magnetically insulated transmission line oscillator （MILO） for the first time which takes a modified HEM11 mode as its main interaction mode. The excitation of the oscillation mode is made possible by carefully adjusting the arrangements of each resonant cavity in a two-dimensional （2-D） slow wave structure. The high frequency characteristics are analyzed and a PIC simulation is carried out; the detailed results are discussed to get a better understanding of this new MILO. Employing an electron beam of about 441 kV and 39.7 kA, it finds that the modified HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz. The power conversion efficiency is about 8.4% and the generated microwave is in a TEll-like circularly polarized mode; its polarization direction is decided by the rotation direction of the SWS.展开更多
Starting friction would be induced and preserved somewhere along the seabed route of cased insulated flowlines（CIF） when the pipe carries service loads.The axial pipe-soil interaction can be divided into three pipe ...Starting friction would be induced and preserved somewhere along the seabed route of cased insulated flowlines（CIF） when the pipe carries service loads.The axial pipe-soil interaction can be divided into three pipe sections：the sliding section,the fixed section and the starting friction section.Although limited to a relatively small length of the pipe,the pipe coats of the starting friction section would suffer much higher shear force caused by thermal expansion than those of the sliding section or the fixed section.Based on the axial equilibrium equation of this kind of insulated pipeline,we developed a method for checking the shear force on CIF coats and their interfaces.The typical example shows that starting friction effect should be taken into account when checking the lap shear strength of heatshrinkable sleeves on CIF field joints.展开更多
The theoretical analysis and actual performance of the single-surface multipactor discharge model in the presence of a magnetic field are conducted through simulations. The effects of the magnitude of the insulated ma...The theoretical analysis and actual performance of the single-surface multipactor discharge model in the presence of a magnetic field are conducted through simulations. The effects of the magnitude of the insulated magnetic field and the oblique incidence of electrons on the multipactor are analysed. The results show that the multipactor susceptibility region shrinks gradually as the magnetic field increases when the electron cyclotron frequency is close to the RF frequency of the electric field. As a result, the evolution of the multipactor discharge will reach saturation earlier and become saturated at a higher level than the case when the magnetic field is absent, but the change of evolution and saturation as the insulated magnetic field increases is not obvious.展开更多
Current loss without an obvious impedance collapse in the magnetically insulated coaxial diode （MICD） is studied through experiment and particle-in-cell （PIC） simulation when the guiding magnetic field is strong e...Current loss without an obvious impedance collapse in the magnetically insulated coaxial diode （MICD） is studied through experiment and particle-in-cell （PIC） simulation when the guiding magnetic field is strong enough. Cathode nega- tive ions are clarified to be the predominant reason for it. Theoretical analysis and simulation both indicate that the velocity of the negative ion reaches up to 1 cm/ns due to the space potential between the anode and cathode gap （A-C gap）. Accord- ingly, instead of the reverse current loss and the parasitic current loss, the negative ion loss appears during the whole pulse. The negative ion current loss is determined by its ionization production rate. It increases with diode voltage increasing. The smaller space charge effect caused by the beam thickening and the weaker radial restriction both promote the negative ion production under a lower magnetic field. Therefore, as the magnetic field increases, the current loss gradually decreases until the beam thickening nearly stops.展开更多
A novel magnetically insulated transmission line oscillator （MILO） in which a modified HEM11 mode is taken as its main interaction mode （HEM11 mode MILO） is simulated and experimented in this paper. The excitation...A novel magnetically insulated transmission line oscillator （MILO） in which a modified HEM11 mode is taken as its main interaction mode （HEM11 mode MILO） is simulated and experimented in this paper. The excitation of the oscillation mode is made possible by carefully adjusting the arrangement of each resonant cavity in a two-dimensional slow wave structure. The special feature of such a device is that in the slow-wave-structure region, the interaction mode is HEM11 mode which is a TM-like one that could interact with electron beams effectively; and in the coaxial output region, the microwave mode is TE11 mode which has a favourable field density pattern to be directly radiated. Employing an electron beam of about 441 kV and 39.7 kA, the HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz in particle-in-cell simulation. The power conversion efficiency is about 8.4 % and the generated microwave is in a TEll-like circular polarization mode. In a preliminary experiment investigation, high power microwave is detected from the device with a frequency of 1.46 GHz, an output energy of 43 J 47 J, and a pulse duration of 44 ns-49 ns when the input voltage is 430 kV450 kV, and the diode current is 37 kA-39 kA.展开更多
In the scope of material science, it is well understood that mechanical behavior of a material is temperature dependent. The converse is also true and for specific loading cases contributes to a unique thermal failure...In the scope of material science, it is well understood that mechanical behavior of a material is temperature dependent. The converse is also true and for specific loading cases contributes to a unique thermal failure mechanism known as “heat explosion”. The goal for this paper is to improve the mathematical models for predicting heat explosion by using a specific case of the Fourier heat transfer system that focuses on thermoviscoelastic properties of materials. This is done by using a computational analysis to solve for an internal heat parameter that determines thermal failure at a critical value. This critical value is calculated under conditions either accounting for or negating the effect of heat dissipated by the material. This model is an improvement on existing models because it accounts for material specific properties and in doing so limits mathematical assumptions of the system. By limiting the assumptions in the conditions of the model, the model becomes more accurate and useful in regards to material design.展开更多
Abstract The magnetically insulated line oscillator （MILO） is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves （HPM） research. In ...Abstract The magnetically insulated line oscillator （MILO） is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves （HPM） research. In order to improve the power conversion efficiency and eliminate or at least minimize anode plasma formation in the load region and radio frequency （RF） breakdown in the slow wave structure （SWS） section, an X-band MILO is presented and inyestigated nu- merically with KARAT code. The design idea is briefly presented and the simulation results are given and discussed. In the simulation, HPM is generated with peak power of 3.4 GW, maximum electric field of about 1 MV/cm, and peak power conversion efficiency of 14.0%, when the voltage is 559.1 kV and the current is 43.2 kA. The microwave frequency is pure and falls in the X-band of 9.0 GHz. The theoretical investigation and the simulation results are given to prove that the anode plasma formation and the RF breakdown can be effectively avoided or at least minimized, respectively.展开更多
A tunable magnetically insulated transmission line oscillator（MILO） is put forward and simulated. When the MILO is driven by a 430 k V, 40.6 k A electron beam, high-power microwave is generated with a peak output po...A tunable magnetically insulated transmission line oscillator（MILO） is put forward and simulated. When the MILO is driven by a 430 k V, 40.6 k A electron beam, high-power microwave is generated with a peak output power of 3.0 GW and frequency of 1.51 GHz, and the relevant power conversion efficiency is 17.2%. The 3-d B tunable frequency range（the relative output power is above half of the peak output power） is 2.25–0.825 GHz when the outer radius of the slow-wave structure（SWS） vanes ranges from 77 mm to 155 mm, and the 3-d B tuning bandwidth is 92%, which is sufficient for the aim of large-scale tuning and high power output.展开更多
To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is u...To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is used for sensitivity analysis of heat insulation layer with different thermal conductivity and thickness,as well as surrounding rock with different thermal conductivity and temperature on a heat-adjusting zone radius,surrounding rock temperature field and wall temperature.The results show that the heat-adjusting zone radius will entirely be in the right power index relationship to the ventilation time.Decrease in thermal conductivity and increase in thickness of insulation layer can effectively reduce the disturbance of airflow on the surrounding rock temperature,hence,beneficial for decreasing wall temperature.This favourable trend significantly decreases with ventilation time,increase in thermal conductivity and temperature of surrounding rock,heat-adjusting zone radius,surrounding rock temperature field,and wall temperature.Sensitivity analysis shows that the thermal physical properties of surrounding rock determine the temperature distribution of the roadway,hence,temperature of surrounding rock is considered as the most sensitive factor of all influencing factors.For the spray layer,thermal conductivity is more sensitive,compared to thickness.It is concluded that increase in the spray layer thickness is not as beneficial as using low thermal conductivity insulation material.Therefore,roadway preferential consideration should be given to the rocks with low temperature and thermal conductivity.The application of the insulation layer has positive significance for the thermal environment control in mine roadway,however,increase in the layer thickness without restriction has a limited effect on the thermal insulation.展开更多
On the basis of on-site measured data of the newly constructed Gonghe-Yushu Highway in a permafrost region, this paper analyzed thermal conditions of the subgrade with XPS insulated board according to different select...On the basis of on-site measured data of the newly constructed Gonghe-Yushu Highway in a permafrost region, this paper analyzed thermal conditions of the subgrade with XPS insulated board according to different selected monitoring sections in various locations. We also summarized the geothermal distribution and change rules of subgrade with XPS insulation board under the asphalt pavement in summarized a high temperature frozen soil region. It is suggested that the shoulder of subgrade with XPS insulation board be widen to a reasonable width so as to keep the subgrade stable.展开更多
基金Project supported by Science and Technology Project of SGCC(Research on Key Technologies for Fault Diagnosis and Early Warning of Intermittent Discharge in UHV GIS:524625200028).
文摘In response to the problem of frequent leakage and false alarm of partial discharge insulation defects in GIS,this paper conducts experimental research on intermittent discharge characteristics of common solid insulation defects in GIS.Using true GIS to build amulti-source testing platform for intermittent discharge of solid insulation defects,and using pulse current method,ultra-high frequency method,ultrasonic method,and gas characteristic component detectionmethod to study the variation law of intermittent discharge characteristics of solid insulation defects.The results showthat:the intermittent discharge state of metal fouling defects on the solid insulation surface decreases with the extension of the discharge time,the discharge time interval as a whole shows an increasing trend,and the metal fouling defects on the solid insulation surface in the intermittent discharge state is difficult to develop into a breakdown discharge fault.The overall discharge amount of air gap defects inside solid insulation also shows the law of increasing first and then decreasing,and the discharge amount of air gap defects inside solid insulation stays at a large level for a long time during intermittent discharge,and there is a risk of breakdown,and the discharge will gradually evolve into continuous discharge;ultrasonic method and characteristic component detection method cannot realize the effective perception of intermittent discharge of metal fouling.The 50-period mapping information commonly used in the power field cannot reflect the intermittent discharge variation law of solid insulation,and the 200-period UHF mapping composed of four groups of 50-period UHF mapping data can initially derive the intermittent discharge distribution law of solid insulation defects.The research results of this paper are of great significance to expand the knowledge of intermittent discharge characteristics and the detection of GIS discharge defects in the field.
基金The National Natural Science Foundation of China(No.61204083)the Natural Science Foundation of Jiangsu Province(No.BK2011059)the Program for New Century Excellent Talents in University(No.NCET-10-0331)
文摘A novel lateral insulated gate bipolar transistor on a silicon-on-insulator substrate SOI-LIGBT with a special low-doped P-well structure is proposed.The P-well structure is added to attach the P-body under the channel so as to reduce the linear anode current degradation without additional process.The influence of the length and depth of the P-well on the hot-carrier HC reliability of the SOI-LIGBT is studied.With the increase in the length of the P-well the perpendicular electric field peak and the impact ionization peak diminish resulting in the reduction of the hot-carrier degradation. In addition the impact ionization will be weakened with the increase in the depth of the P-well which also makes the hot-carrier degradation decrease.Considering the effect of the low-doped P-well and the process windows the length and depth of the P-well are both chosen as 2 μm.
基金supported by the Chinese National Natural Science Foundation (Grant No 10675168)Innovation Fund of Graduate School of the National University of Defense Technology of China
文摘An X-band magnetically insulated transmission line oscillator （MILO） is designed and investigated numerically and experimentally for the first time. The X-band MILO is optimized in detail with KARAT code. In simulation, the X-band MILO, driven by a 720 kV, 53 kA electron beam, comes to a nonlinear steady state in 4.0 ns. High-power microwaves （HPM） of TEM mode is generated with an average power of 4.1 GW, a frequency of 9.3 GHz, and power conversion efficiency of 10.870 in durations of 0-40 ns. The device is fabricated according to the simulation results. In experiments, when the voltage is 400 kV and the current is 50 kA, the radiated microwave power reaches about 110 MW and the dominating frequency is 9.7GHz. Because the surfaces of the cathode end and the beam dump are destroyed, the diode voltage cannot increase continuously. However, when the diode voltage is 400 kV, the average power output is obtained to be 700 MW in simulation. The impedance of the device is clearly smaller than the simulation prediction. Moreover, the duration of the microwave pulse is obviously shorter than that of the current pulse. The experimental results are greatly different from the simulation predictions. The preliminary analyses show that the generations of the anode plasma, the cathode flare and the anode flare are the essential cause for the remarkable deviation of the experimental results from the simulation predictions.
文摘It has been proved that the thermally insulated ocean pipeline has advantages over the conventional pipe-in-pipe pipeline. The risk of using the thermally insulated pipeline is that the exterior layers covering the steel pipe may be. pulled off if the shear stress on the interface induced by the pullout fore from the tensioner is greater than the binding fore between two neighboring layers during installation. This paper develops a procedure to calculate the shear stress on the interface. The binding force between two neighboring layers can be determined with full scale model tests. The safety of the thermally insulated pipe under installation can then be checked by comparison of the interface shear stress with the binding force.
基金supported by National Natural Science Foundation of China(No.10905047)
文摘A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL.
文摘Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this paper, which is one of the most basic ways for diagnosis of insulation condition. Methods Ultra high frequency(UHF) PD detection method by using internal sensors has been proved efficient, because it may avoid the disturbance of corona, but the sensor installation of this method will be limited by the structure and operation condition of GIS. There are some of electromagnetic (E-M) waves leak from the place of insulation spacer, therefore, the external sensors UHF measuring PD technique is applied, which isn't limited by the operation condition of GIS. Results This paper analyzes propagated electromagnetic (E-M) waves of partial discharge pulse excited by using the finite-difference time-domain (FDTD) method. The signal collected at the outer point is more complex than that of the inner point, and the signals' amplitude of outer is about half of the inner, because it propagates through spacer and insulation slot. Set up UHF PD measuring system. The typical PD in 252kV GIS bus bar was measured using PD detection UHF technique with external sensors. Finally, compare the results of UHF measuring technique using external sensors with the results of FDTD method simulation and the traditional IEC60270 method detection. Conclusion The results of experiment shows that the UHF technique can realize the diagnosis of insulation condition, the results of FDTD method simulation and the result UHF method detection can demonstrate each other, which gives references to further researches and application for UHF PD measuring technique.
基金the Major Program of the National Natural Science Foundation of China(Grant No.2009ZX02305-006)the National Natural Science Foundation of China(Grant No.61076082)
文摘In this paper, a novel dual-gate and dielectric-inserted lateral trench insulated gate bipolar transistor （DGDI LTIGBT） structure, which features a double extended trench gate and a dielectric inserted in the drift region, is proposed and discussed. The device can not only decrease the specific on-resistance Ron,sp , but also simultaneously improve the temperature performance. Simulation results show that the proposed LTIGBT achieves an ultra-low on-state voltage drop of 1.31 V at 700 A·cm-2 with a small half-cell pitch of 10.5 μm, a specific on-resistance R on,sp of 187 mΩ·mm2, and a high breakdown voltage of 250 V. The on-state voltage drop of the DGDI LTIGBT is 18% less than that of the DI LTIGBT and 30.3% less than that of the conventional LTIGBT. The proposed LTIGBT exhibits a good positive temperature coefficient for safety paralleling to handling larger currents and enhances the short-circuit capability while maintaining a low self-heating effect. Furthermore, it also shows a better tradeoff between the specific on-resistance and the turnoff loss, although it has a longer turnoff delay time.
基金financially supported by National Natural Science Foundation of China(Grant Nos.51777045 and51477035)Shenzhen Technology Project(Project Nos.JCYJ20160226201347750 and JCYJ20150529115038093)
文摘The intersection point of the characteristic magnetic field line（CMFL） crossing the anode boundary with the discharge channel wall, and its influence on thruster performance and the energy and flux of ions bombarding the channel wall, have been studied numerically. The simulation results demonstrate that with the increase in distance from the crossover point of the CMFL with the channel wall to the bottom of the thruster channel, the ionization rate in the discharge channel gradually increases; meanwhile, the ion energy and ion current density bombarding the channel wall decreases. When the point of the CMFL with the channel wall is at the channel outlet, the thrust, specific impulse, and efficiency are at a maximum, while the ion energy and ion current density bombarding the channel wall are at a minimum. Therefore, to improve the performance and lifetime of the thruster, it is important to control the point of intersection of the CMFL with the channel wall.
文摘This paper introduces the Insulated gate bipolar transistor(IGBT)in- verter for arc welding.The principle of the inverter,the structure and charac- teristics of IGBT and the current feedback system using LEM current transduc- er are discussed.By the measurement of its efficiency and power factor and the tests of welding processes,the developed 150A IGBT inverter proves to be a kind of energy-saving portable power supply for arc welding with broad prospects.
基金Projects supported by the National Natural Science Foundation of China (Grant No. 61176069)the State Key Laboratory of Electronic Thin Films and Integrated Devices,China (Grant No. CXJJ201004)the National Key Laboratory of Analog Integrated Circuit,China (Grant No. 9140C090304110C0905)
文摘A high voltage（〉 600 V） integrable silicon-on-insulator（SOI） trench-type lateral insulated gate bipolar transistor（LIGBT） with a reduced cell-pitch is proposed.The LIGBT features multiple trenches（MTs）：two oxide trenches in the drift region and a trench gate extended to the buried oxide（BOX）.Firstly,the oxide trenches enhance electric field strength because of the lower permittivity of oxide than that of Si.Secondly,oxide trenches bring in multi-directional depletion,leading to a reshaped electric field distribution and an enhanced reduced-surface electric-field（RESURF） effect.Both increase the breakdown voltage（BV）.Thirdly,oxide trenches fold the drift region around the oxide trenches,leading to a reduced cell-pitch.Finally,the oxide trenches enhance the conductivity modulation,resulting in a high electron/hole concentration in the drift region as well as a low forward voltage drop（Von）.The oxide trenches cause a low anode-cathode capacitance,which increases the switching speed and reduces the turn-off energy loss（Eoff）.The MT SOI LIGBT exhibits a BV of 603 V at a small cell-pitch of 24 μm,a Von of 1.03 V at 100 A/cm-2,a turn-off time of 250 ns and Eoff of 4.1×10？3 mJ.The trench gate extended to BOX synchronously acts as dielectric isolation between high voltage LIGBT and low voltage circuits,simplifying the fabrication processes.
基金Project supported by the Science Foundation of the China Academy of Engineering Physics (Grant No 2008B0402046)
文摘This paper puts forward a novel magnetically insulated transmission line oscillator （MILO） for the first time which takes a modified HEM11 mode as its main interaction mode. The excitation of the oscillation mode is made possible by carefully adjusting the arrangements of each resonant cavity in a two-dimensional （2-D） slow wave structure. The high frequency characteristics are analyzed and a PIC simulation is carried out; the detailed results are discussed to get a better understanding of this new MILO. Employing an electron beam of about 441 kV and 39.7 kA, it finds that the modified HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz. The power conversion efficiency is about 8.4% and the generated microwave is in a TEll-like circularly polarized mode; its polarization direction is decided by the rotation direction of the SWS.
文摘Starting friction would be induced and preserved somewhere along the seabed route of cased insulated flowlines（CIF） when the pipe carries service loads.The axial pipe-soil interaction can be divided into three pipe sections：the sliding section,the fixed section and the starting friction section.Although limited to a relatively small length of the pipe,the pipe coats of the starting friction section would suffer much higher shear force caused by thermal expansion than those of the sliding section or the fixed section.Based on the axial equilibrium equation of this kind of insulated pipeline,we developed a method for checking the shear force on CIF coats and their interfaces.The typical example shows that starting friction effect should be taken into account when checking the lap shear strength of heatshrinkable sleeves on CIF field joints.
基金Project supported by the High Power Radiation Key Laboratory Foundation of the National High Technology Research and Development Program of China (Grant No. 20050601)
文摘The theoretical analysis and actual performance of the single-surface multipactor discharge model in the presence of a magnetic field are conducted through simulations. The effects of the magnitude of the insulated magnetic field and the oblique incidence of electrons on the multipactor are analysed. The results show that the multipactor susceptibility region shrinks gradually as the magnetic field increases when the electron cyclotron frequency is close to the RF frequency of the electric field. As a result, the evolution of the multipactor discharge will reach saturation earlier and become saturated at a higher level than the case when the magnetic field is absent, but the change of evolution and saturation as the insulated magnetic field increases is not obvious.
文摘Current loss without an obvious impedance collapse in the magnetically insulated coaxial diode （MICD） is studied through experiment and particle-in-cell （PIC） simulation when the guiding magnetic field is strong enough. Cathode nega- tive ions are clarified to be the predominant reason for it. Theoretical analysis and simulation both indicate that the velocity of the negative ion reaches up to 1 cm/ns due to the space potential between the anode and cathode gap （A-C gap）. Accord- ingly, instead of the reverse current loss and the parasitic current loss, the negative ion loss appears during the whole pulse. The negative ion current loss is determined by its ionization production rate. It increases with diode voltage increasing. The smaller space charge effect caused by the beam thickening and the weaker radial restriction both promote the negative ion production under a lower magnetic field. Therefore, as the magnetic field increases, the current loss gradually decreases until the beam thickening nearly stops.
文摘A novel magnetically insulated transmission line oscillator （MILO） in which a modified HEM11 mode is taken as its main interaction mode （HEM11 mode MILO） is simulated and experimented in this paper. The excitation of the oscillation mode is made possible by carefully adjusting the arrangement of each resonant cavity in a two-dimensional slow wave structure. The special feature of such a device is that in the slow-wave-structure region, the interaction mode is HEM11 mode which is a TM-like one that could interact with electron beams effectively; and in the coaxial output region, the microwave mode is TE11 mode which has a favourable field density pattern to be directly radiated. Employing an electron beam of about 441 kV and 39.7 kA, the HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz in particle-in-cell simulation. The power conversion efficiency is about 8.4 % and the generated microwave is in a TEll-like circular polarization mode. In a preliminary experiment investigation, high power microwave is detected from the device with a frequency of 1.46 GHz, an output energy of 43 J 47 J, and a pulse duration of 44 ns-49 ns when the input voltage is 430 kV450 kV, and the diode current is 37 kA-39 kA.
文摘In the scope of material science, it is well understood that mechanical behavior of a material is temperature dependent. The converse is also true and for specific loading cases contributes to a unique thermal failure mechanism known as “heat explosion”. The goal for this paper is to improve the mathematical models for predicting heat explosion by using a specific case of the Fourier heat transfer system that focuses on thermoviscoelastic properties of materials. This is done by using a computational analysis to solve for an internal heat parameter that determines thermal failure at a critical value. This critical value is calculated under conditions either accounting for or negating the effect of heat dissipated by the material. This model is an improvement on existing models because it accounts for material specific properties and in doing so limits mathematical assumptions of the system. By limiting the assumptions in the conditions of the model, the model becomes more accurate and useful in regards to material design.
基金supported by National Natural Science Foundation of China(No.11075210)the Special Financial Grant from the China Postdoctoral Science Foundation(No.201104761)
文摘Abstract The magnetically insulated line oscillator （MILO） is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves （HPM） research. In order to improve the power conversion efficiency and eliminate or at least minimize anode plasma formation in the load region and radio frequency （RF） breakdown in the slow wave structure （SWS） section, an X-band MILO is presented and inyestigated nu- merically with KARAT code. The design idea is briefly presented and the simulation results are given and discussed. In the simulation, HPM is generated with peak power of 3.4 GW, maximum electric field of about 1 MV/cm, and peak power conversion efficiency of 14.0%, when the voltage is 559.1 kV and the current is 43.2 kA. The microwave frequency is pure and falls in the X-band of 9.0 GHz. The theoretical investigation and the simulation results are given to prove that the anode plasma formation and the RF breakdown can be effectively avoided or at least minimized, respectively.
基金supported by the National Natural Science Foundation of China(Grant No.11075210)the Special Financial Grant from the China Postdoctoral Science Foundation(Grant No.201104761)
文摘A tunable magnetically insulated transmission line oscillator（MILO） is put forward and simulated. When the MILO is driven by a 430 k V, 40.6 k A electron beam, high-power microwave is generated with a peak output power of 3.0 GW and frequency of 1.51 GHz, and the relevant power conversion efficiency is 17.2%. The 3-d B tunable frequency range（the relative output power is above half of the peak output power） is 2.25–0.825 GHz when the outer radius of the slow-wave structure（SWS） vanes ranges from 77 mm to 155 mm, and the 3-d B tuning bandwidth is 92%, which is sufficient for the aim of large-scale tuning and high power output.
基金This work was supported by the National Natural Science Foundation of China(51774011)Funding Project of Anhui University of Science and Technology(QN2019115)Introduced Research Funding of Anhui University of Science and Technology(13190022).
文摘To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is used for sensitivity analysis of heat insulation layer with different thermal conductivity and thickness,as well as surrounding rock with different thermal conductivity and temperature on a heat-adjusting zone radius,surrounding rock temperature field and wall temperature.The results show that the heat-adjusting zone radius will entirely be in the right power index relationship to the ventilation time.Decrease in thermal conductivity and increase in thickness of insulation layer can effectively reduce the disturbance of airflow on the surrounding rock temperature,hence,beneficial for decreasing wall temperature.This favourable trend significantly decreases with ventilation time,increase in thermal conductivity and temperature of surrounding rock,heat-adjusting zone radius,surrounding rock temperature field,and wall temperature.Sensitivity analysis shows that the thermal physical properties of surrounding rock determine the temperature distribution of the roadway,hence,temperature of surrounding rock is considered as the most sensitive factor of all influencing factors.For the spray layer,thermal conductivity is more sensitive,compared to thickness.It is concluded that increase in the spray layer thickness is not as beneficial as using low thermal conductivity insulation material.Therefore,roadway preferential consideration should be given to the rocks with low temperature and thermal conductivity.The application of the insulation layer has positive significance for the thermal environment control in mine roadway,however,increase in the layer thickness without restriction has a limited effect on the thermal insulation.
基金supported by the National Key Basic Research Program of China 973 Project(No.2012CB026104)National Natural Science Foundation of China(No.41271072 and No.51378057)Service Performance Evaluation of the Subsidiary Structure in The Permafrost Regions of the Qinghai Tibet Plateau(2014-07-01)
文摘On the basis of on-site measured data of the newly constructed Gonghe-Yushu Highway in a permafrost region, this paper analyzed thermal conditions of the subgrade with XPS insulated board according to different selected monitoring sections in various locations. We also summarized the geothermal distribution and change rules of subgrade with XPS insulation board under the asphalt pavement in summarized a high temperature frozen soil region. It is suggested that the shoulder of subgrade with XPS insulation board be widen to a reasonable width so as to keep the subgrade stable.
