Given an integral M-currrent To in Rm+k and a tensor H of type(m.l)on Rn+k with values orthogonal to each of its arguments we proved in a previous peper[3]the sxistence of anintegral m-current T =γ(M,θ.ζ)with bound...Given an integral M-currrent To in Rm+k and a tensor H of type(m.l)on Rn+k with values orthogonal to each of its arguments we proved in a previous peper[3]the sxistence of anintegral m-current T =γ(M,θ.ζ)with boundary T0 and mean curvature vector H by minimizing an appropriate functional on suitable subclasses of the set of all integral currents.In thes paperwe discuss the existence and structure of oriented tangent cones C of T at points x∈spt(T) spt(T),especially we show that C is locally mass minimizing.展开更多
Epoxy resin is widely used in high-temperature,high-electric-field power equipment owing to its stable physicochemical properties and excellent insulation performance.During prolonged operation,it undergoes thermal ag...Epoxy resin is widely used in high-temperature,high-electric-field power equipment owing to its stable physicochemical properties and excellent insulation performance.During prolonged operation,it undergoes thermal aging,making lifetime extension essential.The effects of thermal aging on insulation by comparing samples cured with anhydride curing agents under both air and non-air conditions are investigated.The Fourier transform infrared spectroscopy,current integrated charge,and pulsed electro-acoustic methods are used to analyze physicochemical characteristics and electrical performance.Control groups compared thermal aging in air versus an oil bath to examine atmospheric influences.Results show that air-aged samples turned yellow,while the oil bath-aged samples remained colorless.At temperatures above T_(g)(135℃),air-aged samples showed more positive hetero charge accumulation.Non-air-aged samples also accumulated space charge,but to a lesser extent,and sho wed better insulation breakdown resistance.These findings indicate that thermal aging in air may degrade insulation perform ance owing to oxidative effects.展开更多
This paper presents a fully customised integrated gate commutated thyristor(IGCT)gate driver monolithic integrated circuit(GDMIC),aiming to address the many shortcomings of traditional IGCT gate driver units composed ...This paper presents a fully customised integrated gate commutated thyristor(IGCT)gate driver monolithic integrated circuit(GDMIC),aiming to address the many shortcomings of traditional IGCT gate driver units composed of discrete components,such as the excessive number of components,low reliability,and complex development processes.The current-source driving characteristics of IGCTs pose significant technical challenges for developing fully customised integrated circuits(IC).The customised requirements of IGCT gate driver chips under various operating conditions are explored regarding functional module division,power sequencing,and chip parameter specifications.However,existing high-side(HS)driver methods exhibit limitations in functional monolithic integration and bipolar complementary metal-oxide-semiconductor compat-ibility.To address these challenges,a novel HS driving topology based on floating linear regulators is proposed.It can achieve synchronised control of multi-channel floating power transistors while supporting 100%duty cycle continuous conduction.The pro-posed GDMIC reduces the three independent HS power supplies to a single multiplexed topology,significantly decreasing circuit complexity.Experimental results validate the feasibility and performance of a 4-inch gate driver prototype based on IGCT current-source management IC,demonstrating significant advantages in reducing the number of components,enhancing device reliability,and simplifying development.The proposed GDMIC offers an innovative development path for future high-power IGCT drivers.展开更多
文摘Given an integral M-currrent To in Rm+k and a tensor H of type(m.l)on Rn+k with values orthogonal to each of its arguments we proved in a previous peper[3]the sxistence of anintegral m-current T =γ(M,θ.ζ)with boundary T0 and mean curvature vector H by minimizing an appropriate functional on suitable subclasses of the set of all integral currents.In thes paperwe discuss the existence and structure of oriented tangent cones C of T at points x∈spt(T) spt(T),especially we show that C is locally mass minimizing.
文摘Epoxy resin is widely used in high-temperature,high-electric-field power equipment owing to its stable physicochemical properties and excellent insulation performance.During prolonged operation,it undergoes thermal aging,making lifetime extension essential.The effects of thermal aging on insulation by comparing samples cured with anhydride curing agents under both air and non-air conditions are investigated.The Fourier transform infrared spectroscopy,current integrated charge,and pulsed electro-acoustic methods are used to analyze physicochemical characteristics and electrical performance.Control groups compared thermal aging in air versus an oil bath to examine atmospheric influences.Results show that air-aged samples turned yellow,while the oil bath-aged samples remained colorless.At temperatures above T_(g)(135℃),air-aged samples showed more positive hetero charge accumulation.Non-air-aged samples also accumulated space charge,but to a lesser extent,and sho wed better insulation breakdown resistance.These findings indicate that thermal aging in air may degrade insulation perform ance owing to oxidative effects.
基金National Key Research and Development Program of China,Grant/Award Number:2021YFB2401604The Integration Projects of National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid,Grant/Award Number:U2166602National Natural Science Foundation of China,Grant/Award Number:52241701。
文摘This paper presents a fully customised integrated gate commutated thyristor(IGCT)gate driver monolithic integrated circuit(GDMIC),aiming to address the many shortcomings of traditional IGCT gate driver units composed of discrete components,such as the excessive number of components,low reliability,and complex development processes.The current-source driving characteristics of IGCTs pose significant technical challenges for developing fully customised integrated circuits(IC).The customised requirements of IGCT gate driver chips under various operating conditions are explored regarding functional module division,power sequencing,and chip parameter specifications.However,existing high-side(HS)driver methods exhibit limitations in functional monolithic integration and bipolar complementary metal-oxide-semiconductor compat-ibility.To address these challenges,a novel HS driving topology based on floating linear regulators is proposed.It can achieve synchronised control of multi-channel floating power transistors while supporting 100%duty cycle continuous conduction.The pro-posed GDMIC reduces the three independent HS power supplies to a single multiplexed topology,significantly decreasing circuit complexity.Experimental results validate the feasibility and performance of a 4-inch gate driver prototype based on IGCT current-source management IC,demonstrating significant advantages in reducing the number of components,enhancing device reliability,and simplifying development.The proposed GDMIC offers an innovative development path for future high-power IGCT drivers.
