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The role of surge protector

Surge, (Surge protection Device) is an indispensable device in the lightning protection of electronic equipment. The function of the surge protector is to limit the instantaneous overvoltage that enters the power line and signal transmission line within the voltage range that the equipment or system can withstand, or to discharge the strong lightning current into the ground to protect the protected equipment or system from being damaged. damaged by impact.

Surge protector principle

The working principle of the surge protector is as follows: the surge protector is generally installed at both ends of the protected device and grounded. Under normal working conditions, the surge protector presents a high impedance to the normal power frequency voltage, and almost no current flows through it, which is equivalent to an open circuit; when a transient overvoltage occurs in the system, the surge protector will respond to high-frequency transient overvoltages. The voltage presents a low impedance, equivalent to short-circuiting the protected equipment.

1. Switch type: Its working principle is that when there is no instantaneous overvoltage, it presents a high impedance, but once it responds to lightning instantaneous overvoltage, its impedance suddenly changes to a low value, allowing lightning current to pass. When used as such devices, the devices include: discharge gaps, gas discharge tubes, thyristors, etc.

2. Voltage-limiting type: Its working principle is that it is high impedance when there is no instantaneous overvoltage, but its impedance will continue to decrease with the increase of surge current and voltage, and its current-voltage characteristic is strongly nonlinear. Devices used for such devices are: zinc oxide, varistor, suppressor diode, avalanche diode, etc.

3. Shunt type or choke type

Shunt type: in parallel with the protected equipment, it presents low impedance to lightning pulses and high impedance to normal operating frequencies.

Choke type: In series with the protected equipment, it presents high impedance to lightning pulses and low impedance to normal operating frequencies.

Devices used as such devices include: choke coils, high-pass filters, low-pass filters, 1/4 wavelength short-circuiters, and the like.