I. safety capacitor

The definition of safety capacitors: Safety capacitors refer to those used in situations where, if the capacitor fails, it will not cause electric shock and will not endanger personal safety. It includes the X capacitor and the Y capacitor.

II. Definitions of X and Y Capacitors

X capacitor: An X capacitor is a capacitor that spans between two power lines (L-N) and is typically used to filter out differential mode signals.

Y capacitor: A Y capacitor is a type of capacitor that is respectively connected across the two power lines and the ground (L-E, N-E), and is generally u

sed to filter out common-mode signals.

The main difference between these two types of capacitors lies in their connection methods and application scenarios.

III. Model Classification and Parameters

X capacitors are further classified into X1,X2, and X3. The main differences lie in:

X1 high voltage resistance: 2.5KV < X1≤4KV;

X2 high voltage resistance: X2≤2.5KV;

X3 high voltage resistance: X3≤1.2KV;

Under the Y capacitor, there are Y1, Y2, Y3, and Y4. The main difference lies in: (the level of DC voltage resistance)

1.Y1 can withstand high voltage greater than 8 kV.

2. Y2 can withstand high voltage greater than 5 kV.

3. Y3 can withstand high pressure N/A;

4. Y4 can withstand high voltage greater than 2.5kV.

IV. Selecting Elements

When choosing X and Y capacitors, the following factors need to be considered:

Capacitors X and Y must meet the voltage requirements for use. For those exceeding the nominal voltage, they can be used in series to equalize the voltage, but exactly the same capacitors must be used in series.

2. Capacitors X and Y must meet the temperature requirements. The rated temperature of the X capacitor is generally indicated on this body. There are currently two main operating temperatures for Y capacitors: one is -40℃ to +85℃, and the other is -40℃ to +125℃. There is mainly an older type of certification, with the reported temperature range being -40℃ to +85℃. Now, the new safety regulation certification requirements are -40℃ to +125℃.

3. Consider the possible magnitude of the pulse voltage at the input end of the circuit. Different capacitors can withstand different magnitudes of pulse voltage. The withstand voltage of the capacitor must not be less than the peak value of the pulse voltage in the circuit.

4. As safety capacitors, X and Y capacitors must obtain certification from a safety testing institution. The appearance of capacitors is generally marked with safety certification marks (such as UL, CSA, etc.) and the words "Withstand voltage AC250V" or "AC275V". It must be emphasized that X and Y capacitors must not be replaced by ordinary capacitors with nominal withstand voltages such as AC250V or DC400V at will.