Principle of operation of surge protector

Operating principle of surge suppressor

The purpose of installing an SPD (surge suppressor) is to prevent the voltage drop occurring at the load from rising excessively by allowing the current to flow through the surge suppressor itself rather than through the load when a surge current enters the system for some reason. The goal is to protect subordinates by blocking it.

This can be achieved by flowing the surge current through a path with low impedance (i.e. SPD) when a surge enters the system.

MOV is a component that has a very large impedance under normal conditions. When a voltage surge (for example, a voltage exceeding 125% of the rated voltage) is applied, the impedance of the MOV decreases rapidly and becomes a low-impedance path that flows the surge through a path other than the load.

Even if a huge amount of current flows through the surge suppressor, the voltage does not rise significantly.

MOV is the most reliable technology for attenuating surge voltage. Because MOV's clamping characteristics are reliable, more than 95% of SPDs adopt MOV for power supplies.

SAD (Silicon Avalanche Diode) is often used as an SPD for data lines or communication lines.

The representative characteristics of MOV are as follows.

- At normal voltage, almost no current flows.

- When the voltage rises, a lot of current flows.

---> Even if a lot of current flows, the voltage drop does not increase.

Suppresses voltage rise when a huge current flows.

Ex) 1mA at 500V,

10,000A at 1,000V

2 times the applied voltage ===> 107 times the flowing current