Problems in main AC
The environment around an electronic
equipment can affect the way the equipment operates. An electronic equipment may be affected by radio
interference and power-line problems in the electronic
environment. Electronic equipments may also be affected by temperature, humidity, etc, in the
physical environment. You might expect the power company to
guarantee smooth, uninterrupted, electrical power. Unfortunately, the conditions in the power lines to your home
or office are constantly changing. Power problems can be divided into two main category, that is:-
Overvoltage = can be again divided into two types, spikes and surges.
A spikes is a very short burst of high
voltage which can disrupt the operation of any electronic equipments. Some small spikes are caused by switching
equipment, including motor controllers. When lighting strikes the power system, it can cause very large
The effect on electronic equipments varies
with the size and power of the spike. A typical spike may have a fairly high voltage (5000 volts or more). Small
spikes usually do not damage the components, but spikes caused by lighting can be much more powerful. It can
burn the complete PCB of any electronic equipments. As you are troubleshooting, whenever you notice that many
parts are damaged, in different parts of the equipment, suspect lighting damage.
These are overvoltage that last for more
than one cycle. Surges are caused when some heavy electrical load is suddenly switched off. Surges can cause
damage in many equipments.
In case the overvoltage is very severe, it
can slip through the power supply and can blow up the components inside the equipment. A continuous high voltage
can damage the power supply itself.
Spikes and surges are generated by the
switching off of high power motors and other inductive appliances. All electric motors and transformer generate
fields that store energy. When one of these appliances is switched off, the magnetic field collapses and as a
result the stored energy having no other place to go, come down the power line as a spike.
Relatively small motors like those used in
refrigerators, photocopiers and air-conditioners can also lead to spikes of thousands of volts.
Spikes and surges damage any equipment on a
cumulative nature. When a number of spikes and surges get through, first the component and then the electronic
equipments fail. Spikes and surges are the main cause of destruction of the electronic equipments.
Undervoltage = can be further divided into three categories, sags, brownout and
Sags are undervoltage that last for more
than one cycle. Sags can slow down the computer disk-drives, leading to data errors and can cause head crash
making permanent data loss.
Brownout is the low voltage condition that
can be present even for several hours. This is often created when the power demand exceeds the capacitor of the
power generator. Brownout can also cause many problems. Fortunately, high or low voltage problems can be tackled
by using some good quality voltage regulators.
Blackout is the complete no-power condition.
Sometime sudden power failure can bring about wastage of time, money and resources.
The interrupted process may have to be
restarted from some earlier stages or sometimes even the complete work may have to be redone right from the
Any signal present on the power line besides
the expected alternating current of 50 Hz is called the noise. Noise usually consists of short term over and
under voltages. Any noise entering a computer brings about data errors. If the noise is strong enough, it can
get past the power supply and create false digital '1s' and '0s' and can confuse the computer such as cause the
computer to produce a bad bit of data. A few of the letters in a word-processing file may be incorrect, or some
of the numbers in the spreadsheet may be wrong.
There are several different types of noise.
Radio-frequency interference (RFI) is caused by radio or television sources, or even by other computer
equipment. If your equipment is located near a radio or television transmitter, the power or signal lines may
pick up enough of the radio or TV signal to cause problems. A weaker source, such as a wireless telephone,
fluorescent lamp, lamp dimmer, or a car ignition system, can cause similar problems if it close enough to your
equipment. Radio energy drops off very quickly as you move away from the source.
Electromagnetic interference (EMI) can occur
when computer wiring runs too close to equipment that produces an electromagnetic field. As the magnetic field
changes, it can 'induce' false pulses into nearby computer wiring. Again, this effect drops off sharply as you
move away from the source of the EMI. EMI can be a problem when two wires run beside each other. A signal in one
wire can create a changing field, which then induces a signal in the other wire. The effect is stronger when the
wires are close together and when they are parallel for a distance. Large electric motors can create powerful
electromagnetic fields and may cause EMI problems. Electric motors, which may cause EMI, are found in various
kind of equipment-refrigerators, air conditioners, washing machines, furnaces, copier, elevators, machine tools,
and so on.
Harmonic distortion is the deviation of the
power supply waveshape from a pure sinewave. It can disrupt the operation of some sensitive device like
computers and communication equipments.
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Author By : Jestine Yong