Safety Ceramic Capacitor Y1 Type/ Safety Ceramic Capacitor Y2 Type

1: What is the difference between safety capacitors and ordinary capacitors?

The discharge of safety capacitors is different from that of ordinary capacitors. Ordinary capacitors will retain the charge for a long time after the external power supply is disconnected. Electric shock may occur if one touches an ordinary capacitor by hand, while there isn’t such problem with safety capacitors.

For safety and Electro Magnetic Compatibility (EMC considerations), it is generally recommended to add safety capacitors to the power inlet. At the input end of the AC power supply, it is generally necessary to add 3 safety capacitors to suppress EMI conduction interference. They are used in the power supply filter to filter the power supply.

2: What is a safety capacitor?

Safety capacitors are used in such occasions that after the capacitor fails: it will not cause electric shock and will not endanger personal safety. It includes X capacitors and Y capacitors. The x capacitor is the capacitor connected between the two lines of the power line (LN), and metal film capacitors are generally used; the Y capacitor is the capacitor connected between the two lines of the power line and the ground (LE, NE), and usually appears in pairs. Due to the limitation of leakage current, the Y capacitor value cannot be too large. Generally, the X capacitor is uF and the Y capacitor is nF. The X capacitor suppresses differential mode interference, and the Y capacitor suppresses common mode interference.

3: Why are some capacitors called safety capacitors?

The “safety” in safety capacitors does not refer to the capacitor material, but that the capacitor has passed the safety certification; in terms of material, the safety capacitors are mainly CBB capacitors and ceramic capacitors.

4: How many types of safety capacitors are there?

Safety capacitors are divided into X type and Y type.

X capacitors mostly use polyester film capacitors with relatively large ripple currents. This type of capacitor has a relatively large volume, but its allowable instantaneous charging and discharging current is also large, and its internal resistance is correspondingly small.

The capacitance of the Y capacitor must be limited, so as to achieve the purpose of controlling the leakage current flowing through it as well as the impact on the EMC performance of the system under the rated frequency and rated voltage. GJB151 stipulates that the capacitance of Y capacitor should not be greater than 0.1uF.