Until
recently, companies were barely curious in evaluating
UPS before purchase, whereas purchasing a computer
involved detailed appraisal.
The
attitude of the user was that the vendor knew what
was best for the system and was the best judge of
what was required. From the point of view of a professional
installer, a UPS
system was a grudge purchase for most customers
and was quite likely to be added as an afterthought
(usually after several expensive malfunctions had
been diagnosed as power problems).
Nowadays, anyone managing a network knows that uninterruptible
power supplies are essential to save data corruption
and ultimately for saving their company time and money.
If the power to servers is turned off without properly
shutting down the server, data can be corrupted, so
all servers and any PCs that run critical applications
should be protected from power outages. The cost to
the company in the time that it takes to restore the
data from backups, plus the interruption of service
while the server is rebooted, can easily run to thousands
or even hundreds of thousands of pounds per hour.
Besides powering servers when the main electrical
power is lost, UPS also protect against power spikes
(high pulses of energy) and brownouts (a lowering
of voltage without total power loss). UPS can also
provide surge protection for network or telephone
connections. Research on power supply disturbances
conducted in European countries show great differences
from place to place and between different types of
installations. On average a computer site experiences
around 20 blackouts each year which, in general, are
far more common in rural areas. Most blackouts arise
in the local, low voltage distribution network.
An on-line double conversion UPS is a combination
of inverters, rectifiers, specialised electronic controls
and energy storage (for example batteries) constituting
a power system for maintaining continuity of load
power in case of input power failure. The most commonly
used battery, for UPS purposes, is the VR (valve regulated)
lead acid battery. The UPS is designed to ensure that
the battery has a long and trouble-free operation.
Recharging is smooth and the voltage of the total
battery string is kept very stable. Batteries in UPS
will eventually fail.
Too often, administrators discover that the battery
has failed only after the power goes out and the UPS
doesn't keep the system running. New features intended
to combat this problem include monitoring systems
built into the UPS, as well as software to extend
monitoring and reporting capabilities. At the present
time, the commercial mains power supply is not capable
of providing clean and consistent electric power demanded
by sensitive equipment. Such equipment requires a
consistent supply of power of the correct specifications
for their operation, hardware protection, continuity
of process, storage and transfer of information and
safety of personnel.
Computer networks, communication links, electronic
medical equipment, industrial process control, remote
installations like offshore operations, online applications
such as airline reservations, etc, are examples of
such critical loads.
Beyond any dispute the installation of an uninterruptible
power supply (UPS) system is nowadays accepted as
being a vital element in the protection of sensitive
equipment. A UPS uses RS-232 communication to interface
with computer systems. Various details can be interrogated
from the UPS at any time and some messages are automatically
sent from the UPS to the computer. Sophisticated software
in the form of an USHA card (universal SNMP and HTTP
adapter) provides an easy to use sophisticated management
solution offering an interface between the UPS and
the network.
The embedded HTTP server is capable of processing,
forwarding and receiving HTTP commands whilst the
embedded SNMP chips allows the UPS to be monitored
from anywhere on the network rather than only through
the server's serial port. Both facilities can be carried
out simultaneously. An SNMP module also allows the
monitoring of UPS without having to run the UPS software
on the server, and the monitoring of network devices
such as routers or switches where running UPS is not
an option. There are three types of UPS products.
Standby, or "off-line" which provide utility
power during normal operation, line-interactive UPS
which offers a measure of voltage regulation and on-line
UPS which is ideally suited to networks running mission-critical
applications.
On-line supplies a highly stable, low-distortion AC
supply to the critical load, eliminating mains borne
interference altogether. Line-interactive
or Off-line
UPS, whilst boasting gimmicky software, will, however,
only serve to reduce the impact of mains borne interference.
Discerning customers are now switching towards on-line
UPS systems and away from the cheaper line-interactive
or off-line UPS. Technologically, UPS are becoming
far more advanced.
AEC UK's recently launched Power
Station provides up to 12 hours of continuous
power yet takes up to 75% less floor space than traditional
systems. The bespoke system is modular in design and
can be provided in variable support times ranging
from 700VAC to 6kVA to meet customers' specific requirements.
It has been specially engineered to offer ease of
servicing through rapid and easy access to all internal
components.
Field upgradeable in both power and backup times,
the Power Station has full power module hot-swop capability
and a dedicated power charger module, that also includes
extra booster charger, switch gear and charger indicator
light to show that the unit's batteries are functioning
correctly.
Nevertheless, any device that can interrupt this critical
supply will always need an Emergency Bypass
System (EMBS) to allow for maintenance, upgrades
or simply as a fail safe device. The user can easily
install the EMBS, allowing normal mains supply to
be restored in an emergency by bypassing the whole
UPS system. The manual bypass system has a simple
"make before break" rotary switch that reconnects
the load in an emergency or for maintenance or upgrade.
The range of UPS products available makes the choice
of UPS systems somewhat bewildering. Users need to
be knowledgeable so that they are able to be discerning
on the type of UPS required and not fooled by technical
jargon and the over-hyped claims of some UPS manufacturers.
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