INTRODUCTION - WHY A UPS?
We are increasingly dependent on
electrical and electronic equipment in our everyday lives. The proper
functioning of this equipment depends on a good supply of electricity.
Unfortunately, many people wrongly assume that the only time to worry about the
effect of power on computer and other electronic equipment is when there is a
total power cut. Of course this kind of protection is essential and one must
never underestimate the effect total power cuts can have on a business and on
our lives. However, nowadays power cuts in the western world are very infrequent
and what has the greatest impact on businesses are the fluctuations and
disturbances in mains power, which are unseen. Companies need to rid themselves
of the risk of the chance that a power disturbance or blackout could interrupt
their business and yet figures still show that many organisations fail to
protect their business with the correct UPS back up solution.
What a UPS does is not only provide
back up power in the event of complete power failure but also takes the input
electricity, cleans it up and outputs what is called 'pure sinewave'. For the
most part this solution works well for those seeking reliable power protection
and is highly recommended for industries running any kind of mission critical
PARALLEL UPS SYSTEM WHY DO WE NEED IT?
However, as the world around us
continues to change the need for businesses to be up and running 24/7 mean
organisations need an even higher level of reliability. Today, competition,
extended shopping hours, more demanding customers, virtual shopping, mobile
connectivity, the Internet, to name just a few things, have combined to change
the face of the world in which companies and organisations must compete.
To have computer systems, electrical
and electronic equipment, phone lines up and running is now so critical to an
organisation's survival that failure due to power problems cannot be tolerated.
Organisations such as banks, Internet Service Providers, telecommunication
companies and anyone surviving in the thriving e-commerce industry cannot afford
to have their business to go down at anytime. If it does it can lead to loss of
profits and loss of customers perhaps the most damaging effect of all.
For piece of mind they need to know
that their chosen back up solution can never fail. They need to know that if
anything goes wrong with one UPS then another takes over at once. Organisations
need redundancy. And the solution? To run a parallel UPS system.
WHAT IS A PARALLEL UPS SYSTEM?
Put simply a parallel UPS system means
the linking together of two or more UPS units in parallel so that in the
unlikely event one fails the other can automatically take up the load. When
buying a UPS in a situation that requires a redundant solution there are two
types to investigate. You can install a parallel redundant system or an isolated
Redundancy in an isolated (or standby)
system configuration depends completely on the on the successful transfer of the
load by the on-line (primary) UPS to its bypass and the graceful acceptance of
that load by the stand-by (secondary) UPS. Theoretically, it could be a 100%
load step, which is a serious transfer.
To successfully obtain a transfer it
requires the following four step procedure:
The primary unit must recognize that a
transfer is required.
The primary unit must ensure that the
transfer is feasible:
- Bypass source is available
- Bypass source is in sync
* Voltage is within accepted limits
* Frequency is within accepted limits
The actual transfer action has to take
- Static switch must turn on
- The primary unit's inverter must disengage
- If there is a wrap-around breaker, it must close successfully.
The secondary UPS must accept the load
step and maintain a voltage variation within limits that are acceptable to the
critical load. Actually, since the secondary unit is not supporting any load,
one cannot be certain it is operational and will accept the transfer at all
until it is attempted. What a time to find out there is a problem!
These four steps are in series. If any
one of the four steps fail, the transfer fails and the load will be dumped.
Remember, this is an emergency situation. There is no room for a slip. If the
reason for transfer is a faulted bus, the transfer must take place TWICE before
the load bus is attached to a power source capable of clearing the fault
(through the bypass of the secondary UPS). If the reason for transfer is a
failed primary UPS, the module cannot be isolated for repair because the
secondary UPS is feeding the load through the bypass of the primary UPS. If
there is a maintenance bypass, the load can, of course, be transferred to it but
if UNPROTECTED power is acceptable, why spend the money for redundancy?
A parallel redundant systems, and the
systems which Powerware Power Systems strongly supports, has a number of
advantages that increase the availability of protected power to the load and
gives the customer fewer things to worry about where support of the critical
load is concerned.
With a parallel redundant system the
following six points outline the advantages:
two most critical elements in the isolated redundant scheme are eliminated:
Execution and Acceptance of the load transfer
Qualification stage is minimised because the normal operation of a parallel
redundant configuration is for the modules to share the load, which means they
must be in sync for both voltage and frequency.
a module is taken off line for maintenance, the remaining module AT WORST will
suffer a 50% load step, which substantially reduces the risk of voltage
variations outside the limits of the critical load (its safe to say the risk is
eliminated). You can be sure the on-line module is operational and will accept
the transfer because it is already sharing the load.
unit that is off-line is isolated so maintenance can be performed.
Protected power to the load is maintained by the on-line unit and automatic
transfer to bypass is still an option if necessary.
a faulted bus occurs, only one transfer is required to reach a power source (the
feeder bus) capable of clearing the fault.
To make a parallel system work you will
always rely on the transfer to bypass happening successfully with the secondary
module always accepting the load gracefully. But if it doesn't you are back to
where you started. A parallel redundant system eliminates the possibility of
HOW TO PARALLEL? REDUNDANCY AND
When installing a parallel redundant
system, in other words to get two or more units to run parallel and share the
load the units must be locked to exactly the same phase. You must then
synchronise the modules, connect them together through the collective buses of
the system thus allowing them to share the load between them.
The system is now ready to achieve
redundancy. Load the system with power equal to the total demand of all the
loads minus the demand of a least one module. This ensures that failure of any
one UPS will not corrupt the power, will allow one to isolate the damaged module
whilst the functioning UPS modules seamlessly take over without the load ever
noticing the transfer.
Doesn't all this sound great. However
we still have one problem. Traditionally a parallel redundancy configuration is
achieved by having a common paralleling logic circuitry in the system. This
logic circuitry gives out individual commands to all the different units.
Unfortunately this can lead to a single point of failure for the whole system
because if the logic circuitry system fails the whole UPS system will be in
trouble. And so what you are left with is a very complicated configuration that
at the end of the day and whilst this gives you a 98% solid power protection it
does not eliminate the risk of a single point of failure keeping you from
receiving 100% peace of mind.
That is exactly why the Powerware Hot
Sync( technology was developed. An industry leading paralleling technology in
its own right, the patented Hot Sync( enables you to setup a parallel redundant
system giving you 100% conditioned power at all times. Its unique digital design
eliminates the system-level single point-of-failure inherent in traditional
parallel UPS modules and exponentially increases the reliability of the overall
HOW DOES IT WORK?
Hot Sync allows two or more UPS units
to cover the same load in parallel and redundant configuration, by working in
complete synchronisation without being wired together. No common logic is needed
in this patented design. It provides automatic load sharing and module level
redundancy with nothing other than the power connecting the modules.
Hot Sync does not require any
centralised commands to function. All units are able to function on their own
and make decisions simply by looking at their own output, the UPS modules do not
need any communication between them to load share or to remove a faulty module
from the load bus. If one module fails the other or others continue supplying
the load and the failed UPS module is immediately isolated from the critical bus
while the other UPS takes over the full load. This means there is no single
point of failure, no crashes and most importantly no downtime. In short the
critical load remains 100% UPS protected.
It manages to share the load by making
minute changes to the output phase angle 1000 times per second. If one of the
UPS modules detects that it is getting ahead of the other it will push its extra
load back to the other module until finally the load is evenly shared. If the
load changes all UPSs will see it instantaneously and in the same the way.
That's why an even load share is maintained even if the load varies.
Phenomenal growth of super-servers,
telecommunication switching centres, and other large, centralised computing
operations, has created a market need for extremely large power solutions. This
need typically exceeds the capacity of a single UPS module. To address this
shortfall, Hot Sync( enables UPS modules to be tied together to create a UPS
solution that protects the entire system, and allows additional modules to be
added as capacity needs grow. It allows customers to expand effortlessly from a
single-module system to a two-module redundant system and, potentially, to an
eight-module system. The scalability of this system provides customers the
flexibility to add the power protection as their application grows. And it also
makes redundancy for these very large systems a reality, increasing system
availability and overall reliability.
A globally recognized industry leader
for more than 40 years, Powerware designs and manufactures a full line of
Uninterruptible Power Systems (UPS), DC power systems, power management
software/connectivity products. Powerware products are typically used in
networking, PC, financial, medical, industrial, voice and data communications,
military and aerospace applications - wherever continuous power is essential to
daily operations. Powerware is headquartered in Raleigh, NC, and is part of
The company offers a full range of UPSs
ranging in size from 300 volt-amperes (VA) for personal computers to greater
than 1,000 kilovolt-amperes (kVA) for mission-critical applications including
data centers, Internet service providers, and server farms. Network-connectivity
devices, extended battery cabinets, power distribution modules and other
power-related devices further enhance Powerware UPS hardware offerings. The
Powerware product portfolio also includes a full line of DC Power Systems
ranging in size from mini systems for roadside cabinets or customer premises
equipment to large systems for major switching installations. Power management
software and IT infrastructure management software complete the company's
product line. Basic power management software provides industry-standard
monitoring, alarm and shutdown capabilities. More advanced software packages
offer expansive data archiving, trending and regression analysis tools with
predictive capabilities. With innovative software that can predict the type and
timing of possible future events, Powerware is leading an industry shift from
reactive power protection to proactive power management.
Eaton Corporation is a diversified
industrial manufacturer with 2003 sales of $8.1 billion. Eaton is a global
leader in fluid power systems and services for industrial, mobile and aircraft
equipment; electrical systems and components for power quality, distribution and
control; automotive engine air management systems and powertrain controls for
fuel economy; and intelligent drivetrain systems for fuel economy and safety in
trucks. Today, the company classifies its business into four distinct segments,
which are, by size: Fluid Power, Electrical, Automotive and Truck. Eaton has
51,000 employees, 207 manufacturing sites and sells products to customers in
more than 100 countries.
GemNet is a power solutions company,
providing quality power products and services. Our philosophy has always been to
combine its local expertise and commitment with quality products, technical
competence and the support of its principal. Since inception, it has been our
goal to build deep and long lasting relationships with our customers and
alliance partners by providing them top-quality power products and services.
This has been the single most important success factor for GemNet, earning it
the reputation as one of the leading and most professional power products and
solutions companies. Today, GemNet enjoys an established track record of
excellence with its customers in Pakistan and the United Arab Emirates. GemNet
is the authorized distributor for Eaton Powerware's range of AC and DC
Uninterruptible Power Systems, and offers a large range of specialized power
related products and services. The company has local offices in Karachi, Lahore
and Islamabad (GemNet Pvt. Limited) and Dubai, United Arab Emirates (GemNet
AREAS OF EXPERTISE:
*Service plans to fit the clients
needs, including plans that cover the client's existing Power Systems and UPSs.
*Services also include: Needs Analysis,
Comparative Product Analysis, Cost Justification, End-User Training,
Maintenance, After Sales Support, Data/telecom center electrical contracting and
* Power Consulting & Critical
Environment Site Audit (CESA): Audit of existing UPS and recommendation of a
power solution. Analysis of the quality of power feeding the systems.
Facility/Site inspection, identification and correction of the problem.