Effect of short circuit switching on dielectric properties of vacuum interrupters
Short circuit current interruption may change the dielectric properties of vacuum interrupters during their service life. Therefore, in this work effects of the current interruption on the dielectric properties and contact erosion of the interrupters have been investigated. Contact material's evaporation during the flow of the vacuum arc before current zero may change the contact surface and cause some erosion after each operation. With the help of field electron emission current measurement the surface conditions of the interrupter contacts are compared between the new vacuum interrupters and interrupters which were previously subjected to interruptions with different arc current amplitudes and arcing time. With the help of Fowler-Nordheim diagram, surface parameters i.e. field enhancement factor β and emission area Ae are calculated and compared for each case. Field electron emission current inception voltage and breakdown voltage are compared for these cases as well.
Insulation Properties of Vacuum Interrupters after Short-Circuit Current Interruption
Effect of the short circuit current interruption on the insulation properties and contact erosion of the vacuum interrupters have been investigated. Contact material’s evaporation during the flow of the vacuum arc before current zero may change the contact surface and cause some erosion after each operation. With the help of field emission current measurement the surface conditions of the interrupter contacts are compared between the new vacuum interrupters and interrupters which were previously subjected to current interruption. With the help of FowlerNordheim diagram, surface parameters i.e. field enhancement factor β and emission area Ae are calculated and compared for each case. Field emission current inception voltage and breakdown voltage are compared for these cases as well.
CAUSES OF FLUCTUATIONS IN R&D EXPENDITURES A QUANTITATIVE ANALYSIS
Introduction 124 The stylised facts of R&D in OECD economies 124 The determinants of business R&D expenditures 127 Modelling R&D expenditures 130 Conclusion 135 Bibliography 137 Annex: The model 138