A capacitor that is used in an AC primary circuit for electromagnetic interference suppression is required to be compliant with the safety standards of the countries concerned.
Generally, the electric equipment that is used with AC power supply may stay plugged in. Therefore, a capacitor for electromagnetic interference suppression used between the lines or between the line and earth line may be subjected to severe conditions such as surge voltage from a lightning strike along with constantly applied AC voltage.
Moreover, from a safety perspective, when using a capacitor it is necessary to consider that capacitor failure can result in electric shock or fire.
To comply with safety regulations, select safety standard certified capacitors certified by the following certification bodies and under the following safety standards.
Major certification bodies and safety standards
|U.K.||BSI||EN 132400/IEC 60384-14|
Select a capacitor from suitable subclass satisfying the safety requirements of the equipment.
Capacitors of class X (inserted between lines of power supply circuit)
voltage in service
voltage Up applied
（when CN≦1.0μF ）
|X1||> 2500 V
≦ 4000 V
|4000 V||4.3UR (d.c.)
|X2||≦ 2500 V||II||General
Capacitors of class Y (inserted between a line of power supply circuit and the earth or enclosure)
|Subclass||Type of insulation
|Range of rated
|Peak impulse voltage
Up applied before
|Y1||Double insulation or
|≦ 500 V||8000 V||4000 V (a.c.)|
|Y2||Basic insulation or
|UR + 1200 V (a.c.)
with a minimum of
1500 V (a.c.)
UR: rated voltage
|Y4||Basic insulation or
|< 150 V||2500 V||900 V (a.c.)|
NOTE The details is referred to IEC 60384-14:2013. The voltage proof test is according to Test A.