The power you get from the wall outlet is known as
"120 volts AC power." It can be represented by a sine wave of voltage, as
shown. The power companies try to keep that voltage uniform. Lightning,
short-circuits, poles knocked down by cars, or some other accident can make the
voltage jump to hundreds, even thousands of volts.
The voltage spike shown is what engineers call a
"surge." A surge will last only a few millionths of one second (the "blink of
an eye" is thousands of times longer than the typical surge). It is enough to
destroy or to upset your appliances.
What can a surge do to your
appliances?
Your appliances are designed to run on the normal 120
volts AC supply, with some tolerance for more or less, but they can be damaged,
or their controls can be upset by surges. The result is then frustration and
repair bills, and even a fire in rare cases.
See the next section for a
discussion of how sensitive your appliances can be to these surges.
Don't give up!
You can do something about it, your
electrician can help and even the power company can offer help, as this booklet
will show you -the why's and how's.
Other disturbances. . .
. . . and what they can do to your
appliances
In the normal operation of a power system,
unavoidable disturbances other than surges also happen. They can upset
electronic appliances, but are unlikely to cause permanent damage. This booklet
is concerned with surges and how to protect your appliances against surges.
However, just to give you an idea of what these other disturbances can be, the
graphs and words below will give you the right words when you want to discuss a
problem with your power company, your electrician, and (hopefully, not any
longer) an electronics repair shop.
Normal - This is the voltage that we all
take for granted, every second of the minute, every minute of the hour, every
hour of the day, every day of the year. But occasionally, for a short
time...
The voltage falls below normal: a sag.
Sags are unlikely to damage most appliances, but they can make a computer
crash, confuse some digital clocks and cause VCRs to forget their settings.
The reverse of a sag is called a swell:
a short duration increase in the line voltage. This disturbance might upset
sensitive appliances, and damage them if it is a very large or very long swell.
Noise is a catch word sometimes used to
describe very small and persistent disturbances. These do not have damaging
effects but can be a nuisance.
There is, of course, the ultimate disturbance: an
outage -no voltage at all!
These disturbances are different from surges, but
they should be mentioned because the remedies are generally different. As we
will see later, some available devices can help overcome both.
