Surge Suppressor Fundamentals

Electronic equipment may have many paths of entry for harmful surge voltages. These paths range from the low voltage AC line. Neutral or ground circuitry, to data I/O or telecommunication lines. The surge causes damage by appearing as overvoltage (voltage potential difference across an electronic circuit or device). When this voltage potential exceeds the rating of a component within the circuit, the component "shorts out" and usually, "follow on" current causes additional havoc in the circuit. These voltage potentials may occur from line to neutral, line to ground, neutral to ground, data line to data line, data line to ground, or data line to power mains. When one is considering protection for equipment, all doors or paths of entry should be examined and/or protected.

Surge suppressors limit the voltage potential by "turning on" when a preset voltage is reached and then absorbing part of the energy of the surge and eventually diverting all surge energy to ground. Once the surge has been dissipated, the suppressor "resets" and waits for the next surge. Crucial in the design of a suppressor is its ability to turn on rapidly and absorb or divert all the energy present in the surge and clamping or holding the "let through" overvoltage down to a level safe for exposed circuitry.

Most of todayís sophisticated electronic equipment in industry, office and home environments will experience shortened life ranging from the immediate catastrophic failure to latent failure (days to years) due to electrical overstress if left unprotected.

Poorly designed and "low end" surge suppressors may help equipment that is exposed to minor surge voltages, however, average and severe voltage overstress will eventually cause shortened equipment life and failure. This is due to the rise of "let through" voltage that occurs during a surge of larger amplitude. The overvoltage is caused by the inability of the suppressor to absorb or divert all of the surge energy present on the line.

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