Abstract: A new FB - ZVT - PWM converter is proposed. The new converter operates at a fixed frequency and implements ZVS for power devices without increasing voltage in both turn - on and turn - off transient. A 80 kH...Abstract: A new FB - ZVT - PWM converter is proposed. The new converter operates at a fixed frequency and implements ZVS for power devices without increasing voltage in both turn - on and turn - off transient. A 80 kHz/50 W FB - ZVT - PWM boost converter using MOSFETs is analysed theoretically.展开更多
In the present paper, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, and X-ray diffraction （XRD） were used to examine the effects of a Sr-Y composite modifier on the microstructure ...In the present paper, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, and X-ray diffraction （XRD） were used to examine the effects of a Sr-Y composite modifier on the microstructure of A356 alloy. After adding Y to A356, YAl 3 compounds formed, and the size of the α （Al） crystal nucleus increased. The degree of supercooling caused by Sr-Y composite modifier was higher than Sr modification by 2.7 °C, leading to an increased nucleation rate. This increase in supercooling temperature was favorable to the refinement of eutectic structure of the alloy and its eutectic reaction was delayed to the maximum extent. The Si phase in the as-cast Sr-Y composite-modified A356 alloy was either granular or flaky. No large flakes of eutectic Si were found, and the modification effects were completely comparable with those obtained using a lone Sr modifier. After T6 heat treatment, most of the eutectic Si showed a grain-like shape with smaller grains. No eutectic Si with long-strip shapes, significant enhancements in the particle roundness and evenness of the Si crystals, and increased globosity were observed. Both the roundness and evenness of the grained Si crystals were enhanced, and the amount of globular eutectic Si available increased, these findings showed that excellent modification effects were achieved.展开更多
文摘Abstract: A new FB - ZVT - PWM converter is proposed. The new converter operates at a fixed frequency and implements ZVS for power devices without increasing voltage in both turn - on and turn - off transient. A 80 kHz/50 W FB - ZVT - PWM boost converter using MOSFETs is analysed theoretically.
基金Project supported by National Natural Science Foundation of China(51141007)
文摘In the present paper, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, and X-ray diffraction （XRD） were used to examine the effects of a Sr-Y composite modifier on the microstructure of A356 alloy. After adding Y to A356, YAl 3 compounds formed, and the size of the α （Al） crystal nucleus increased. The degree of supercooling caused by Sr-Y composite modifier was higher than Sr modification by 2.7 °C, leading to an increased nucleation rate. This increase in supercooling temperature was favorable to the refinement of eutectic structure of the alloy and its eutectic reaction was delayed to the maximum extent. The Si phase in the as-cast Sr-Y composite-modified A356 alloy was either granular or flaky. No large flakes of eutectic Si were found, and the modification effects were completely comparable with those obtained using a lone Sr modifier. After T6 heat treatment, most of the eutectic Si showed a grain-like shape with smaller grains. No eutectic Si with long-strip shapes, significant enhancements in the particle roundness and evenness of the Si crystals, and increased globosity were observed. Both the roundness and evenness of the grained Si crystals were enhanced, and the amount of globular eutectic Si available increased, these findings showed that excellent modification effects were achieved.
