Rui Longyuan Electronics
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Rui Longyuan Electronics
Rui Longyuan Electronics
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Circuit protection of AC mains - overvoltage and overcurrent

Circuit protection for AC mains

Design Notes:
Protection application:
Products directly connected to the AC mains (120 to 250VACrms) are often more likely to be exposed to severe surge transient environments (such as lightning, load switching, etc.) than DC current input products, and are more likely to encounter short circuits and overload conditions. Therefore, the function of the protection device needs to be more powerful.
Solution description:
As shown in the upper left figure, tubular or leaded fuses (Pico5x20mm, 2AG, 3AG, TE5 / TR5) can be used for protection under short circuit and overload current conditions. For surge protection, use a varistor. The varistor should be selected based on the severity of the transient surge (energy, voltage, and peak pulse current) to which it may be subjected. The specific series of varistor (C-III, UltraMOV or LA) can be determined after understanding the severity of the surge.

Supporting solutions: Not applicable.
Regulatory issues:
The standard also changes depending on the product being protected. Standards include: IEC 61000-4-5 UL1414 UL1449
Characteristics: Not applicable.
Application warning:
When selecting a fuse, be sure to consider the temperature of the fuse's working area and the inrush current. Inadequate consideration of these factors can lead to premature or incorrect tripping of the fuse.