Safety capacitor refers to a safety capacitors that will not cause electric shock after the capacitor fails and does not endanger personal safety. Safety capacitors are usually only used for filtering in anti-interference circuits. They are used in power supply filters to play the role of power supply filtering, respectively filtering common mode and differential mode interference. For safety and EMC considerations, it is generally recommended to add safety capacitors at the power inlet.
The discharge of the safety capacitors is different from the ordinary capacitor. The charge of the ordinary capacitor will remain for a long time after the external power supply is disconnected. If you touch it by hand, you will be charged, but the safety capacitors does not have this problem. At the input end of the AC power supply, generally need to add three safety capacitors to suppress EMI conducted interference.
Safety capacitors are divided into x-type and y-type. The AC power input is divided into 3 terminals: live wire L/neutral wire N/ground wire G, (L=Line, N=Neutral, G=Ground). Between the “LN”, that is, between the “FireWire-Neutral” is the X capacitance; between the “LG/NG”, that is, between the “FireWire-Ground or Neutral-Ground” is Y capacitance. Connecting a capacitor between FireWire and Neutral is like “X”, and connecting a capacitor between FireWire and Ground is like “Y”, these are not divided according to what material.