Surge Protector: A Simple Mechanism Description

Written By: T.L. McMullen

A surge protector [AKA surge suppressor] is an electrical plug-in device designed to distribute safe electrical voltages to other electrical or electronic devices. Surge protectors resemble power strips in appearance; however, they are more sophisticated and deliver a constant, continuous power supply.

In addition to connecting multiple devices to a single power source, surge protectors provide protection from frequent problems that plague conventional utility power. The most common of these problems are surges (temporary increase of voltage) and brownouts (temporary decrease of voltage). These disturbances slowly degrade many power supply units and cause premature equipment failure. The rising demand on our nations power grids is causing more brownouts than ever before (Gamble; Power Protect Your Computer).

The Inside of a Surge Protector

Toroidal Choke Coil: The toroidal choke coil is an electromagnet wrapped in wire. It filters out line noise as the hot wire passes through it.

Metal Oxide Varistors (MOVs): An MOV has three parts: a piece of metal oxide material in the middle and two semiconductors joined to the hot and ground wire. As a protective connecting unit it shifts unsafe voltage levels to the ground wire.

Neutral Wire: The neutral wire is common in modern wiring practices for safety. It is used in conjunction with the hot wire and the ground wire.

Hot Wire: The hot wire holds the passing current which contains excess voltage.

Fuse: A fuse is a resistor used to protect the wiring from getting too hot. Fuses blow or burn out, thereby preventing the electrical current from traveling further.

Ground Wire: The ground wire protects users from getting an electrical shock. It receives excess voltage from from the MOVs.
Most surge protectors contain a parallel circuit design whereby the extra voltage is fed away from the standard path to another circuit. Another design is a series circuit where the electrical current is slowed; moreover it detects high voltage, stores the electricity, and releases it gradually (Harris).

The majority of the electrical currents diversion is done through the metal oxide varistor or MOV. The MOV acts as a pressure-sensitive valve: based on the level of voltage, the electrons in the semiconductors behave differently either creating lower or higher resistance. When the voltage is correct, an MOV doesnt do anything (Harris).

Specifications and Quality Considerations

Energy Absorption: Surge processors are measured in joules (the amount of energy they can absorb). The higher the number, the better the protection: 200 joules provides basic protection, 400 is good and 600 or high is superior protection.

UL1449: Standard rated by Underwriters Laboratories as the minimum protection standards for surge protectors. It rates suppressors by the amount of voltage passage they allow.

Protection Indicator: LED indicator as to metal-oxide varistors functioning. MOVs do not last forever one lightening strike can fry them out.

Line Conditioning: Most surge protectors contain this feature. It filters out line noise using a toroidal choke coil to condition the current.

Power Switch: There are manual on/off power switches as well as circuit switches. Circuit switches are useful for keeping some components running while others are shut off.

Circuit Breaker or Fuse: A fuse is a resistor that can conduct current below a certain level. If the current is higher than acceptable, heat burns the fuse and cuts off the circuit. Breakers are more economical than fuses as they do not have to be replaced.

Protection Guarantee: Read the terms and conditions carefully! It is important to understand your consumer rights in the event of damage to devices your surge protector neglects to protect (Kozierok).

According to data published on Hewlett Packards website, recent statistics reveal 63 percent of all electronics casualties are the result of a power related problem. Most affected are devices using computer chips and high-speed microprocessors. Unprotected computers can suffer hardware degradation and extensive damage when exposed to power surges (Power Protect Your Computer).

The cost of a surge protector varies greatly depending on user needs. Basic models sell for as low as $10 but one should be cautious as to the capabilities these units offer.

NOTE: It is important to connect all peripheral equipment to the surge protector for complete protection. This includes phone jacks, modems, cables, and any other external devices that will receive electrical current.

All visuals have been removed from this article to comply with the publishing rules for this site.

Additional Resources

Gamble, T. Storm Season www.bestbuy.com 15 Sep. 2004

Harris, T. How Surge Protectors Work
www.computer.howstuffworks.com 15 Sep. 2004

Kozierok, C.M. External Power Problems www.pcguide.com 15 Sep.
2004, http://www.pcguide.com/ref/power/ext/probs.htm

Power Protect Your Computer, www.hp.com 15 Sep. 2004

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