Capacitors are widely used in pulsed magnet power supplies to reduce ripple voltage,store energy,and decrease power variation.In this study,DC-link capacitors in pulsed power supplies were investigated.By deriving an ...Capacitors are widely used in pulsed magnet power supplies to reduce ripple voltage,store energy,and decrease power variation.In this study,DC-link capacitors in pulsed power supplies were investigated.By deriving an analytical method for the capacitor current on the H-bridge topology side,the root-mean-square value of the capacitor current was calculated,which helps in selecting the DC-link capacitors.The proposed method solves this problem quickly and with high accuracy.The current reconstruction of the DC-link capacitor is proposed to avoid structural damage in the capacitor’s current measurement,and the capacitor’s hotspot temperature and temperature rise are calculated using the FFT transform.The test results showed that the error between the calculated and measured temperature increases was within 1.5℃.Finally,the lifetime of DC-link capacitors was predicted based on Monte Carlo analysis.The proposed method can evaluate the reliability of DC-link capacitors in a non-isolated switching pulsed power supply for accelerators and is also applicable to film capacitors.展开更多
Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunn...Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunnel length was only a function of the turn-on interval of DC. The potential of Al foil broke at on-off controlling DC by the result from anode polarization curves and potential-time （E-t） responding curves. When DC was switched on, the potential increased abruptly over pitting potential, leading to nucleation of pits at the surface and the growth of tunnels at special length. When DC was switched off, the potential decreased rapidly to a passive value, leading to stoppage of nucleation and death of tunnels. By this way, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Hence, etching of Al foil at this current is beneficial for maintaining a good mechanical strength.展开更多
Ti species have been deposited on low-voltage etched aluminum foils by a simple electrochemical method using a Ti anode as Ti source in a Ti-free I2-dissolved acetone solution. After annealing at 500-600℃ in air, an ...Ti species have been deposited on low-voltage etched aluminum foils by a simple electrochemical method using a Ti anode as Ti source in a Ti-free I2-dissolved acetone solution. After annealing at 500-600℃ in air, an Al2O3-TiO2 composite oxide film was formed on the surface of the etched aluminum foil by anodizing galvanostatically in an ammonium adipate solution. The effects of I2 concentration in the acetone solution, applied anode voltage, electrolysis time, and annealing temperature on the specific capacitance of the aluminum anode foils were investigated. The TiO2-deposited specimens prepared by applying a po-tential of 50V for 3 min in 2.5m MI2-added acetone solution followed by annealing at 550℃ after anodization exhibited the highest specific capacitance, with an enhancement of 22% compared with pure etched aluminum foil specimens. The electro-deposition process and the change of the anode voltage during the anodization were analyzed.展开更多
基金supported by the National Key Research and Development Program of China(No.2019YFA0405402).
文摘Capacitors are widely used in pulsed magnet power supplies to reduce ripple voltage,store energy,and decrease power variation.In this study,DC-link capacitors in pulsed power supplies were investigated.By deriving an analytical method for the capacitor current on the H-bridge topology side,the root-mean-square value of the capacitor current was calculated,which helps in selecting the DC-link capacitors.The proposed method solves this problem quickly and with high accuracy.The current reconstruction of the DC-link capacitor is proposed to avoid structural damage in the capacitor’s current measurement,and the capacitor’s hotspot temperature and temperature rise are calculated using the FFT transform.The test results showed that the error between the calculated and measured temperature increases was within 1.5℃.Finally,the lifetime of DC-link capacitors was predicted based on Monte Carlo analysis.The proposed method can evaluate the reliability of DC-link capacitors in a non-isolated switching pulsed power supply for accelerators and is also applicable to film capacitors.
基金This study was financially supported by Beijing Education Commission,China.
文摘Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunnel length was only a function of the turn-on interval of DC. The potential of Al foil broke at on-off controlling DC by the result from anode polarization curves and potential-time （E-t） responding curves. When DC was switched on, the potential increased abruptly over pitting potential, leading to nucleation of pits at the surface and the growth of tunnels at special length. When DC was switched off, the potential decreased rapidly to a passive value, leading to stoppage of nucleation and death of tunnels. By this way, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Hence, etching of Al foil at this current is beneficial for maintaining a good mechanical strength.
基金supported by the National Natural Science Foundation of China (21021002 & 51072170)
文摘Ti species have been deposited on low-voltage etched aluminum foils by a simple electrochemical method using a Ti anode as Ti source in a Ti-free I2-dissolved acetone solution. After annealing at 500-600℃ in air, an Al2O3-TiO2 composite oxide film was formed on the surface of the etched aluminum foil by anodizing galvanostatically in an ammonium adipate solution. The effects of I2 concentration in the acetone solution, applied anode voltage, electrolysis time, and annealing temperature on the specific capacitance of the aluminum anode foils were investigated. The TiO2-deposited specimens prepared by applying a po-tential of 50V for 3 min in 2.5m MI2-added acetone solution followed by annealing at 550℃ after anodization exhibited the highest specific capacitance, with an enhancement of 22% compared with pure etched aluminum foil specimens. The electro-deposition process and the change of the anode voltage during the anodization were analyzed.
