Causes and hazards of surge over voltage
Surge protectors are commonly used devices to limit lightning surge overvoltage, and are commonly used in 220V/380V power supply systems. According to different working principles, surge protectors can be divided into voltage switch type surge protectors and voltage limit type surge protectors.
1. Voltage switch type surge protector
The voltage switch type surge protector presents a high impedance when there is no surge, and when a voltage surge occurs, it changes to a low impedance. This type of protector can reduce the overvoltage to close to zero, but it must have a large current flow capacity. Common devices used as such surge protectors are effective discharge gaps, gas discharge tubes, thyristors and triacs.
2. Voltage-limited surge protector
Voltage-limited surge protectors present high impedance when there is no surge, but their impedance will continue to decrease as the surge current and voltage increase. This type of protector presents a certain voltage when passing the surge current, which is called residual voltage or clamping voltage. Common devices used as such surge protectors include metal oxide varistors and transient voltage suppression diodes.
Three, application scenarios
1. Surge protectors are usually connected in parallel with the protected equipment, and their function is to release overvoltage energy and limit the overvoltage to a level that the protected facility can withstand.
2. Different use conditions have different requirements for the devices used in the surge protector. As a rough protection, the protection device installed near the entrance of the external circuit requires a large flow capacity, but a higher residual voltage is allowed. As a fine protection device, the device used for the protection of internal circuit solid components requires a lower limiting voltage, and its current capacity may be lower.
3. "Surge" refers to the sudden overvoltage and the accompanying large current. The surge protector can also play a role in limiting the transient overvoltage caused by electromagnetic induction and operation, so it can also be called an overvoltage limiter. The overvoltage limiter used in high voltage power system is called lightning arrester