What is the maximum capacitance value of a Y-shaped capacitor

What is a Y-shaped capacitor? Y-type capacitors are a series of safety capacitors, which are used in situations where the failure of the capacitor will not cause electric shock and will not endanger personal safety. The Y-type capacitor includes Y1 capacitor and Y2 capacitor.
Y-type capacitors are a unique device in power circuits, especially in ACDC converters where they play a significant role in suppressing common mode interference. Y-shaped capacitors can usually be placed in the following places.

1. At the input end, a filter is formed with a common mode inductor, and L and N are added to PE respectively.

2. The positive and negative terminals of the energy storage capacitor are applied to the PE.

3. Add PE to the output end.

4. Transformer primary and secondary side bridging.

The Y-shaped capacitor is connected between the phase line and the ground line, and belongs to the safety regulation capacitor. In order to not exceed the allowable leakage value of the grounding wire specified by relevant safety standards, the value of these capacitors is approximately a few nF, with a common 10nF being considered relatively large, which is 103.

The capacitance of a Y-shaped capacitor must be limited in order to control the magnitude of the leakage current flowing through it and its impact on the EMC performance of the system under the rated frequency and voltage. GJB151 stipulates that the capacity of Y-type capacitors should not exceed 0.1uF. In addition to meeting the corresponding grid voltage withstand voltage requirements, Y capacitors also require sufficient safety margin in electrical and mechanical performance to avoid breakdown and short circuit phenomena in extremely harsh environmental conditions. The withstand voltage performance of Y capacitors is of great significance for protecting personal safety.