- A surge protector is a device designed to protect computers and other sensitive electronic circuits from bursts of excessive current, called surges. Electricity normally comes into a house at a steady voltage of 120 volts. Although electric current can vary a little, when it rises too high it can damage or destroy circuitry quickly. Surge protectors prevent this from happening by diverting excess power and shutting off power altogether as a backup.
- Most surge protectors divert surges to a ground wire, which allows the current to flow safely into the ground. One way to do this is through a metal oxide varistor or MOV. The MOV is attached between the power supply and ground. Normally, it resists the flow of electricity so much that no current passes through it to ground. When the voltage gets high, however, the resistance of the MOV drops and it conducts extra current away from the circuit. Some circuits use a gas tube to do the same thing. The tube has an inert gas between two electrodes. When the voltage is at a normal level, it can't flow through the gas but when it spikes, the current ionizes the gas, making it able to conduct the electricity to ground.
- Although surge protectors can divert some extra electricity to the ground, this ability is limited. A big or prolonged surge will have more power than the ground wire can conduct. Because of this, surge protectors usually have a backup system to stop current from flowing if they can't divert enough power. The most common way to do this is with a fuse. A fuse is a small filament encased in a glass tube. When too much current flows through the fuse, it heats up and disintegrates, breaking the circuit. Generally, this destroys the circuit breaker, but it also may save the equipment plugged in to it.
