A high-voltage surge on a power line can destroy electronics in a fraction of a second. Although a home or commercial power outlet typically delivers between 110 to 120 V, on rare occasions it briefly rises to thousands of volts -- far beyond the safe operating range for electronic equipment. You can protect your electronics with a variety of devices that prevent high-voltage energy from causing damage.
Because homes and businesses depend on reliable power, power companies strive to keep power line voltage tightly regulated; however, conditions such as lightning, bad wiring and the operation of industrial equipment are beyond the utilities' control. A lightning strike near a power transformer, for example, induces a pulse of electrical and magnetic energy in the equipment. In a few millionths of a second, the transformer undergoes a rise of thousands of volts, and the lines connected to the transformer carry this surge into homes and offices. Although a surge typically lasts only a few thousandths of a second, it carries enough energy to burn out sensitive electronic components.
The lowest-cost option for high voltage protection of electronics is the surge suppressor, commonly found in power strips and other electronic equipment. The surge suppressor is a device called a Metal Oxide Varistor, a component that changes its electrical resistance in response to a sudden rise in voltage. Under normal conditions, the MOV has a high electrical resistance and plays no role in an electrical circuit. When the voltage exceeds a rated value, the MOV's resistance drops in a few trillionths of a second. Because current takes the path of least resistance, the MOV traps the surge and dissipates its energy. Although a severe surge will destroy an MOV, it is less expensive to replace than the electronic equipment it protects.
Constant Voltage Transformers regulate the voltage of the electric power passing through them. The CVT's input connects to a large-amperage power outlet; its output has standard AC outlets into which you plug your electronic equipment. Although more expensive than a surge suppressor, a CVT eliminates minor brownouts and other temporary voltage fluctuations in addition to blocking surges. A CVT makes sense when you need to protect expensive and electrically sensitive electronics.
An Uninterruptible Power Supply is a device that provides backup electricity when the main power fails. When the AC line voltage falls below a threshold value, such as 100 V, the UPS automatically turns the direct current, or DC, stored in an internal battery into 60-Hz AC, or alternating current, that's suitable for computers, medical electronics and other critical equipment. The UPS switches over rapidly, so the equipment keeps running without interruption. In addition to battery backup capability, a UPS protects against high-voltage surges.
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