If the voltage between the plates of a capacitor rises, passing over a certain value, breakdown occurs. The dielectric turns into a conductor and the capacitor is damaged by the produced spark. The maximum voltage that can be applied to a capacitor without causing rupture of the dielectric is called breakdown voltage and is calculated as follows:
Formula 1
Vr = Ds x d
Where:
Vr is the breakdown voltage in kilovolts (kV)
Ds is the dieletric strength in kV/mm
d is the distance between the plates in millimeters (mm)
Derivated Formulas:
Formula 2
Ds = Vr / d
Formula 3
d = Vr / Ds
Application Example:
Calculate the highest voltage that can be applied between the plates of a capacitor formed by two plates separated by a distance of 5 mm and using a piece of glass as dieletric.
Data:
D = 5 mm
Ds = 20 kV/mm (table 15)
Vb = 1
Using formula 1:
Vb = 20 x 5 = 100 kV
