Basic Components of the Surge Protector

What is a Surge Protector?

Surge protection device is generally composed of two gap rods exposed to the air separated by certain distance, wherein the power supply phase of a metal rod is connected with a desired protection equipment line L1 or zero is connected to the line (N), and another metal rod and the ground wire (PE) is connected, when the transient overvoltage hit the gap breakdown, part of the over-voltage charge enter the earth to avoid the protected equipment voltage rises. Such a discharge gap distance between the two metal rods can be adjusted according to needs, the structure is relatively simple, and the drawback is the arc extinguishing performance is poor. Surge protection device is widely used in mobile communication base station, the Microwave Communications Authority (station), telecommunications room, plant, civil aviation, finance, securities and other DC power system protection.

MOV Varistor

The varistor is a metal oxide semiconductor non-linear resistor used the ZnO as a main component, when the voltage acting on it reaches a certain value, and then the resistance is very sensitive to the voltage. It works the equivalent of multiple semiconductor PN series and parallel. Chip varistor is characterized by non-linear characteristics (I = CUα the nonlinear coefficient α), flow capacity (to 2KA/cm2), normal leakage current (10-7 to 10-6A), residual depression (depending on the operating voltage of the varistor and the through-flow capacity), response time (~ 10-8s), freewheeling transient overvoltage. Varistor main technical parameters: pressure-sensitive voltage (i.e. switching voltage) UN Reference voltage Ulma; residual voltage Ures; residual voltage ratio K (K = Ures / UN); maximum through-flow capacity Imax; leakage current; Response Time. Maximum reference voltage varistor should be determined by the withstand voltage of the protection of electronic equipment, varistor residual depression is lower than the protected electronic equipment and loss voltage levels.

Gas Discharge Tube in the Surge Protector

The gas discharge tube is consisted of in the glass tube or ceramic tube away from one another a pair of cold cathode plate package filled with an inert gas (Ar). In order to improve the probability of triggering of the discharge tube, there is also discharge trigger agent in the electric tube. This inflatable discharge tube is diode-based and three-pole type, the main technical parameters of the gas discharge tube are: DC discharge voltage Udc; impulse discharge voltage Up (Up in the general case ≈ (2 to 3) Udc; power frequency withstand current In; impulse withstand current Ip; the electrode capacitance insulation resistance R (> 109Ω); interelectrode capacitance (1-5PF). The gas discharge tubes can used in DC and AC conditions.

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