More
reasons for having a UPS
The majority of businesses would be
affected greatly if there was an unexpected power
failure, many would be unable to operate at all.
Total mains failure, more commonly known
as blackouts, has in the past caused companies
to collapse. Though this may have disastrous consequences
there are many other problems to consider; E.g. power
surges, power cuts, radio
singles interfering and much more. This can have
an effect on most electrical equipment, most commonly computers.
It is essential that some computers and electrical systems
run uninterruptedly in order to keep a company operating
These ‘electrical loads’ need a power source
that is more constant and dependable than most to certify
that operation is maintained.
Uses in critical situations:
Due to the quantity of equipment based
on microprocessors becoming commonplace in industry, the
amount of equipments that are now classed as critical
loads is constantly increasing. As on-line sales
rapidly become an endless, twenty-four hour a day business
a need for clean filtered power with no downtime has emerged.
Common problems with you power
supply:
Spikes:
A spike is a short but rapid
voltage change which distorts the mains waveform.
Spikes can occur in both positive and negative form and
can inflict damage or destruction to electric equipment.
These are more often than not as result of thermostats or
alternative apparatus swapping high electrical currents.
The most severe trigger of spikes is when grounded
lightening strikes, it is most serious when it hits telecommunication
cables. Both hardware and software can be badly
damaged as a result of spikes. Exposing sensitive electrical
devices to high voltages will without doubt produce extensive
damage to hardware. However in the long-term, damage to
software can be much more costly this is because regularly
read files may become corrupted and system processing may
complex the problem further.
Electrical Noise:
Problems with common mode electrical
noise can cause computers to ‘hang’ and on occasion
corrupt important data. This difficulty is caused
by a disturbance taking place between supply lines and earth.
Noise happening when in normal mode is a result of a disturbance
that can be caused by many conditions including lightening
striking or radio frequency equipment interfering close
by. These conditions instigate a problem between
line-to-line and line-to-neutral creating electrical noise.
Vulnerable circuits that make use of the supply earth as
reference for internal control logic can often be effected
by high- frequency noise energy which is entering to earth
line. Interference of the manner is not only produced through
mains but can also arise from some external connections
such as communication cables. There are various ways to
minimise the occurrence and damage of this common problem,
for example surge suppression filters can be fitted to the
equipment and the implementation of accurate and appropriate
cable screening can also help.
Surges:
A voltage surge can be described
as; a continual voltage increase that is higher than the
standard mains value also this can often last for more than
just a single cycle. A surge can lead to system
failure by corrupting the switched mode power supply apparatus
of a computer. Surges generally take place following
a large load being turned off or a load swapping at substations.
Sags:
A Sag is the complete opposite
of a surge, it is a dramatic drop in the main supply and
like the surge it is capable of lasting numerous cycles.
These also have similarities to the negative spike (see
spikes) from a generation angle but they do have much longer
time duration. These are extremely common incidents; they
are as a rule triggered off by the turning on of a large
load. If the mains voltage drops to an extreme low the computer
equipment may believe that it has been switched off and
therefore re-boots itself.
Harmonics:
These are dangerous as they
can initiate a inconsistent increase in current which causes
an escalation in temperatures, this often ends
in the overheating of apparatus and more worryingly, component
malfunction .Harmonics are brought about by currents that
are dragged from the mains by non-linear equipments. Photocopiers
and laser printer are some of the equipments which are capable
of causing this nature of disturbance as they contain controlled
rectifiers. The trouble with harmonics is that
they build-up slowly inside computers and progress as a
business develops and increases the amount of PC’s
in a company building. Harmonics produce a great deal of
heat and in the most severe of cases this may devastate
the site’s main neutral busbars. It is essential to
purchase a UPS that has a low input current THD (total harmonic
distortion.)
Blackouts:
A blackout,which can have an
extremely damaging and destructive effect, this occurs when
there is a complete collapse of the mains power supply which
results in total power loss. A series of situations can
set off a major blackout including thunderstorms and supply
line faults.
Brownouts:
These are similar to sags, mentioned
earlier; the one difference is that a brownout lasts much
longer and is usually far more serious. When a mains supply
is not capable of managing with the load demand and the
producing business drops the network voltage a brownout
may occur. In the worst of situations these brownouts can
last for several hours at a time.
Summing
up common problems with your power supply
A load that is used in a critical situation
can be affected by a many different power problems that disturb
the running of a business. The biggest problem attached to
all of these interferences is their irregularity and unpredictability.
As a result of this randomness any action taken to protect
vital equipment has to be in operation continuously when the
load is being used. IT equipment generally have upper and
lower voltage limits which typically allow for between +/-
5 - 10% variation from the standard supply voltage, but will
accept short variations beyond those limits.
Greater excursions can be endured by equipments, when the
duration period of the excursion is shorter. Some computers,
due to the design of their internal power supply, are capable
of riding out voltage sags or interruptions of up to approximately
10ms, although not all units are capable of this. It departments
wanting systems’ reliability most have both a consistent
and clean supply.
The
Solution:
After
a load is employed in what is viewed as a critical situation,
the grounds for protecting it from electrical interference
are great. Nevertheless the individual function of each
UPS will determine the required amount of protection. If
suitable filters are added and in the supply line an isolation
transformer is fitted, many power problems such as spikes
and electrical noise disturbance could be avoided. Some
exterior apparatus can be connected in order to reduce the
risk of Surges occurring. Blackouts, brownouts or any complete
power loss have are much more serious, as a results each
equipment’s requirements must be assessed individual.
Some loads can fail due to a few milliseconds of power interference
while other equipment can cope for a much longer duration
without any damage being done. Each load has different supply
requirements, for example take into account the dissimilar
needs of an air-conditioning system to a telecommunication
network or a life support machine. In some instances, including
the latter, installing a back-up generator might be a necessity.
If the equipment is being used in a constant 24-hour a day
cycle, it is absolutely essential to install a Uninterrupted
Power Supply (UPS) to provide consistent and clean power.
