How to calculate the leakage current of Safety Capacitor?

Leakage current is an important parameter for capacitors. Taking the safety capacitor VJ2220Y472KXUSTX1 from Vishay as an example, we’ll explain how to calculate this value.

Although the datasheet does not directly specify the a value for leakage current, we can still calculate this parameter using Insulating Resistance (IR) if the insulating resistance is specified in the datasheet.

VJ2220Y472KXUSTX1 Insulating Resistance:

For this Vishay 4700pF capacitor, the minimum IR is 100Gohm (at +25oC). The maximum leakage current can be obtained from the relationship between the test voltage and the insulating resistance.

  • Maximum leakage current = Voltage ÷ IR

Although the voltage rating of this capacitor is 250Vrms, it can withstand the DC voltage exceeding 1kVdc. In general, for the voltage greater than 500Vdc, the industry standard IR test voltage is 500Vdc.

For 500Vdc test voltage, leakage current = 500Vdc ÷ 100Gohm = 5nA (maximum). However the leakage current is usually much smaller than this value.

Testing method: Apply a voltage of 500Vdc and a 20 second soak time to show an average leakage current. Longer soak time will yield even lower levels of leakage current.