You are here: HomeTechnical InfoInsulation Resistance
and plastic film capacitors usually have insulation
resistance values ranging from 6000 to 12000 M.
The insulation resistance is given
in Ohm. This is not quite explicit
because the insulation resistance changes for a time after voltage is applied - the
self-discharge constant = Ris x C is also used to measure the quality of the
The time constant gives the time in
seconds during which the voltage between the terminating
wires of a charged capacitor decreases to 37% due to
With capacitance values in the µF range, the time
constant at the time of delivery is usually between 2000
and 4000 seconds.
Humidity which penetrates into the capacitor winding,
lowers the insulation resistance.
An appropriately thick casing should therefore be
provided, according to how much humidity the capacitor
will be subjected to.
Good insulation resistance
is necessary for capacitors which are used to block off
DC voltage and for storage capacitors in which a
particular voltage rate has to remain unchanged for a
longer period of time.