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Definition: surge suppression


Diverting or diminishing excessive current from the AC power line, which can damage sensitive electronic equipment. Power surges generally last less than 50 microseconds but can reach 6,000 volts and draw 3,000 amps when they arrive at the equipment. Shunt mode and series mode are the two types of surge protection.

Shunt Mode - Divert
The most common method is the use of a metal oxide varistor (MOV), which acts like a pressure relief valve to divert the surge to neutral and/or ground. However, shunt mode methods can be problematic. Diverting high voltage to ground may damage equipment because all electronic devices are interconnected via ground. In addition, MOVs can stop working without warning because there are countless low-energy surges occurring all the time, each one causing a minuscule degradation in the MOV. If the MOV is high quality, it can take decades to fail. However, poorly made MOVs can stop working much sooner.

Series Mode - Block and Absorb
Series mode surge protectors actually block high current and absorb excessive voltage, limiting the surge to acceptable levels. Series mode units can activate the suppression as soon as the voltage goes over the norm instead of waiting for a high surge. In 1989, Zero Surge, Inc., Frenchtown, New Jersey, pioneered series mode technologies. See voltage regulator, UPS, power surge, power swell, spike and sag.




Shunt and Series Hybrids
Hybrid surge protectors use both shunt and series modes such as this American Power unit. Capacitors absorb low-energy surges, while the MOVs divert the high energy. (Image courtesy of American Power Conversion Corporation.)







All Series Mode
Zero Surge units use coils and capacitors to absorb the energy and release only acceptable levels to the equipment. There are no parts that degrade with each surge encountered.






Keep Running Smoothly
To safeguard a UPS such as this APC unit, it is plugged into a series mode suppressor dedicated entirely to the UPS. The high energy of a surge is brought down to low levels before it reaches the UPS.