(^330) PC Hardware: A Beginner’s Guide
Power Surge A power surge, which is also called an over-voltage event,
increases the voltage outside normal levels like a spike, but for longer periods
of time. A power surge can begin as a spike, but instead of dropping off as
suddenly as it came, it slowly drifts back to normal levels. Power surges are
usually caused by sudden increases in line voltage on the AC power system.
For instance, should a large nearby electrical user suddenly drop its power, it
would cause a surge over the system.
Brownouts A brownout is a dro pin the voltage in the incoming AC power that
lasts for some time. A brownout is the opposite of a surge, except where the spike
is quickly over, the brownout can last for several seconds or longer. If the voltage
drops too far or lasts too long, its effect on the PC can be the same as a blackout.
Noise Electrical noise on the AC power line can be caused by electromagnetic
interference (EMI) and radio frequency interference (RFI). The exposed AC power
lines act like antennas to pick up EMI and RF signals emitted by computer
monitors, fluorescent lighting, electrical motors, radio transmitters, and lightning.
Protecting the Power Supply
There are a number of devices you can use to protect your PC and its power supply from
the problems associated with AC power. The range of these devices is from essentially
one-time surge protection to full-battery backup with line conditioning.Surge Suppressors
Most plug strips advertised for computer use also include some capability to protect the
devices plugged into them against a power spike or surge. These devices are interchange-
ably calledsurgesuppressorsandsurgeprotectors (Figure 14-11). A surge suppressor is rated
inJoules,whichisameasurementoftheamountofelectricalsurgethedevicecanabsorb.
Surge suppression devices have a built-in component, a metallic oxide varistor
(MOV), to divert the over-voltage power to a grounding circuit. An MOV is a one-time
device. Once the MOV has been hit with a power surge, it is essentially not there and will
have no effect on any future surges. However, there are some surge suppressors with
advanced technologies, such as gas discharge tubes and pellet arrestors, that can handle
more than one event.UPS Devices
A UPS (uninterruptible power supply) is also referred to as a battery backup and standby
powerdevice.However,UPSdevicescanalsoprovide,dependingonthemodelandhow
much you pay for it, surge suppression and even line conditioning. The UPS is essentially
a large battery and a battery charger. It provides a PC protection against short-term
power outages, surges, spikes, and brownouts.
A UPS helps provide a constant, reliable, and nonfluctuating stream of AC power by
monitoringtheACpowerlineandprovidingvoltagefromitsbatterywheneverthevoltage
of the AC line is below a certain level. The UPS also hel pbuffer s pikes and surges by
storing off any voltage above a certain level as well.