Treść książki
Przejdź do opcji czytnikaPrzejdź do nawigacjiPrzejdź do informacjiPrzejdź do stopki
Uinc2=8.6kVinthesecondcaseforthe3.7kV/mmelectricfield.Thisinterplayimpacts
theoccurrenceofPDpulses(Fig.3.15b)and,asvisualizedforτ1>τ2inFigure3.15a,
resultsintp2>tp1.
b)
a)
Fig030150Influenceofcavitythickness(1.3mm–red;2.3mm–blue)onrecovery
voltagebuild-upandtimetpbetweenconsecutivePDpulses:
a)cavitychargingvoltage;b)PDpulses(Uext=2.5kV)
ThiseffectisevenmorepredominantwhenraisingthePDextinctionvoltage
from2.5kV(Fig.3.13)to4kV(Fig.3.15).Thevoidsurfaceconductivitystronglyde-
pendsonthePDdynamicsinpolymericmaterials;thus,surfaceerosionandagingleads
togreatermaterialsurfaceconductivity(ergo,alowerPDextensionvoltage).
Duetothepartialdischarge,voltagedropΔUonvoidcapacitanceCcequals
Δ
U
=
U
inc
−
U
ext
(3.30)
TheextinctionvoltagerepresentsthechargeQneutralizationconditionsinthedis-
chargesource.
Q
=Δ⋅
UC
c
(3.31)
ExtinctionvoltageUextcanassumeacertainvalue(Uext≠0)dependingonthe
surface-dischargingdynamicsinthedischargesource.Dependingontheextinction
voltagelevel,thevoid-chargingvoltagecanassumethewaveformsshowninFig-
ures3.15and3.16.
57
