More Surge Protector (surge protection) Information
Surge
protectors are the primary defense you have to protect your sensitive
electronic, computer, and stereo equipment from electrical surges or
electrical spikes caused primarily by your power company, storms, and
by internal electrical fluctuations within your home or office
building. Internal causes can occur whenever equipment in a building
is suddenly energized, like an elevator or air conditioning
compressor; at home it can be when the refrigerator starts or washing
machine changes cycles. These electrical surges or spikes usually
only last for a short time, often less than a full electrical cycle
which is 1/60 of a second, but over time repeated electrical spikes
or power surges have a cumulative effect and will work to deteriorate
electronic components which can eventually fail.
Surge
protectors can be built with one or more of the following
electronic components:
- A
fuse burns out or circuit breaker trips when excessive power is
being consumed and fed to a device. These can protect both from
surges caused by the device itself and from external surges that
last long enough.
- An
iron poor transformer can transmit AC power similar to a normal iron
core transformer (although less efficiently), but will be unable to
transmit sudden surges that saturate the small iron core.
- A
MOV is a small device that will short out when presented with a
sufficiently high voltage, hopefully passing the surge to ground
through the MOV rather than through the protected device.
Unfortunately, these devices tend to self destruct (and are
therefore one-shot devices) with sufficiently strong surges. Many
cheap surge protectors only have MOV's, and probably will not
survive even a single lightning strike.
- A
zener diode is a small diode designed to protect against normal
spikes in a circuit, especially motor controller circuits. These are
sometimes paired as a transient voltage suppression diode.
- A
gas discharge tube is used much like a MOV, except that it relies on
a trapped gas to become ionized to pass the voltage. This has the
advantage of being able to pass much more power without self
destructing, but with the disadvantage of reacting to the high
voltage more slowly.
- An
Uninterruptible power supply (in addition to other surge protection
devices listed above) typically passes external power past the
unit's battery, which will absorb spikes much like a capacitor in
parallel acts as a low pass filter. (This also keeps the battery
charged, and in the event of a failure, the battery can continue to
supply power without any interruption otherwise needed to switch it
in.) Typically these are the best ones, but are also more expensive.
Voltage
spikes are fast, short duration surges (overvoltages) in the
electric potential in
a given circuit. These are typically caused by lightning
strikes,
although power outages, tripped circuit breakers, short circuits, and
power transitions in other large equipment on the same power line,
and malfunctions caused by the power company can also cause them.
While technically, the pulse produced by a nuclear explosion
detonation
produces a voltage spike, these rare events are commonly referred to
as an electromagnetic pulse (EMP).
The
effect of a voltage spike is to produce a temporary increase in
current flow.
For sensitive electronics this
can cause excessive current flow. In /
semiconductor
junctions,
the voltage may exceed the reverse breakdown potential,
thus destroying or severely weakening the device. A transient voltage
suppression diode, transil, varistor, or a range of other overvoltage
protective
devices can be used to minimize this damage.
While
generally referred to as a voltage spike, the phenomenon in question
is actually a power spike, in that it is measured not in volts
but
in joules. The root cause is the rapid buildup and decay of a
magnetic field, which will induce whatever
voltage on the lines as is necessary to pass the given quantity of
energy. Most
equipment damage from surges and spikes can be prevented by the use
of surge protection equipment.
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