UPSonNet
 | |  | |  | |  | |  |
| Spread Your Word On the Globe |
 | |  | |  | |  | |  | |  | |  | |  | |  | |  | |  | |  |
| UPSonNet NewsLetter October 2011 |
UPSonNet
| | | | | | | | |
| Spread Your Word On the Globe |
| | | | | | | | | | | | | | | | | | | | | | |
To View Articles Sign In / Sign UP |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
UPSonNet
| | | | | | | | |
UPS Upgrading: Costs & Gains
When UPS Turns Power Down
| Spread Your Word On the Globe |
How much to Pay for Best UPS
Backup Battery & UPS Reliability
| | | | | | | | | | | | | | | | | | | | | | |
Best UPS Battery Technology
UPS Waveform & New Computers
UPSonNet
Specifying the Right Off Line UPS
How to Drop a Protected Computer
| | | | | | | | |
5 Nines Three Phase Scalable UPS
| | | | | | | | | | | | | | | | | | | | | | |
Redesign UPS & Boost Efficiency
Life Expectancy of UPS Batteries
| The Best UPS for Today and Tomorrow |
Editorial Topic by Meir Portnoy: How to Select The Best UPS to Protect Legacy and New
Computers.
Energy Star, an International Standard of Energy, issued in October 2011 a new version of UPS
Specification and Test Method standard, which will become effective by April 2012. The
specification defines new requirements for UPS systems including such items as minimum
Efficiency and input Power Factor levels that UPS manufacturers should meet.
The standard, which aims to fulfill Energy Star mission to protect the environment through
superior energy efficiency, was based on study of existing UPS systems performance. The study
included legacy systems as well as new systems designed to meet latest international green oriented
standards needed to protect new computers and critical loads, which are also designed to increase
efficiency and decrease environmental pollution.
We are now at the turning point, where UPS systems are required to protect both legacy
computers, which are still existing and offered on the market, and modern type computer loads.
Whereas modern UPS systems can be designed and programmed to operate with all types of loads,
legacy UPS systems, which are still actively produced and marketed, may not operate satisfactory
with new computers, and may even cause damages when connected to new type loads.
Therefore, a wrong answer to the question, which is the best UPS to choose for today and
tomorrow, may have a dramatic impact on the ability to select a UPS which provides the right
protection to our existing critical equipment, as well as to the new equipment which the new UPS
will be required to protect?
To help solving the problem the following, non exhaustive, UPS characteristics should be
considered, when selecting a UPS for current and future needs:
UPS High Efficiency Operating Mode
Increasing efficiency is the main aim of recent green oriented trends and legislations as well as the
interest of every UPS customer in order to reduce running electricity costs of the UPS systems and
the associated cooling expenses.
Off Line UPS systems, such as Backup, Standby or line Interactive offer inherently high efficiency
by providing normally the utility voltage directly to the load. Online solutions however,
characterized by double conversion power processing, have additional losses wasted on the power
conversion components. Although manufacturers, succeeded to boost average UPS efficiency of
double conversion systems, from 88 - 92% a decade ago to about 94 - 96% today, it us still behind
the 98% offered by Offline systems.
To increase the efficiency of Online systems further, an Off Line topology under the name of Eco
or High Efficiency mode was adopted by numerous UPS manufacturers. The idea is to work
normally from the line transferring to double conversion mode whenever the utility exceeds allowed
limits.
The Eco mode solution has the reliability of an Off Line system, and may cause load dropping or
failure in case of mains high voltage transients due to the inability of static switch to transfer the
load fast enough to the inverter, or in case that the inverter has latent failures, revealed only when
utility fails and load is connected to the UPS inverter.
All UPS systems with Eco mode regime enable the user to deselect the Eco mode, and select
continuously double conversion mode of operation. The problem starts when users procure the
UPS systems based on the tempting high efficiency default figure, finding out about the Eco mode
after a load failure has occurred.
UPS Output Waveform
The Input current waveform of most legacy loads protected by the UPS is a pulsed type
waveform, which can be synthesized by a series of sinusoidal waveforms, commencing with the
fundamental line frequency, followed by infinite series of odd harmonic waveforms.
Only the fundamental ( line) frequency term of UPS output current contributes to net power able to
produce work, all other higher frequency waveforms are parasitic harmonics which cause losses
and pollution of the utility without any real contribution. Total (or Apparent) power defined in
Volt-Ampere (VA) units is derived by multiplying line voltage by total amperage, which includes the
fundamental waveform and all harmonics, whereas Active Power defined by Watt units is derived
in a typical pulsed waveform by multiplying the line voltage by the component of the current with
the fundamental (line) frequency.
The ratio of Watt to VA is called Power Factor (PF), and is equal to 0.6 - 0.7 at the input of most
legacy computers. Latest green legislations require elimination of harmonics which pollute the input
line, achieved by increasing input PF of computers and servers by means of an Active Power
Correction (APFC) circuit. Such circuits need however sinusoidal input voltage as provided by the
utility line and by most double conversion UPS systems.
A problem rises when such loads are connected to almost all Standby and most Line interactive
UPS systems, which provide a non sinusoidal voltage waveform from the internal inverter that
supplies power from the batteries when line power fails. Such UPS systems, which work fine with
legacy computers and servers, may cause malfunction and even harm, when connected to new
electronic equipment equipped with APFC power supplies.
UPS Power Rating
Output power factor of a UPS is another term of confusion, which users should consider when
selecting UPS protection. UPS systems are designed to provide the needed power to the critical
load at the lowest cost. Hence, legacy UPS systems designed to protect legacy loads with low input
Power Factor are designed to offer also low output power factor.
For decades UPS systems were rated in Volt Ampere units. A 1000 VA UPS had Output Power
Factor of about 0.7 designed to protect a typical load without APFC which requires only 700Watt.
New Loads however with APFC have an input PF of almost one, such 1000VA load requires a
UPS with unity power factor, designed to provide 1000Watts.
For proper protection both UPS VA and UPS Watt ratings must be higher than the respective load
figures. However, most UPS systems on the market, and particularly single phase systems, are still
designed to protect legacy computers without APFC, and have an output power factor of 0.7.
A user considering procuring UPS systems should therefore prefer a high output power factor
UPS, able to protect both legacy and new computer loads. Unfortunately, in most cases unaware
users, connect new servers with APFC power supplies, to an existing UPS system with low output
power factor. Such connection will affect the capability of the legacy UPS to supply the power
required by the new server systems and the batteries' capability to provide the needed autonomy
time.
UPS Ability to Protect Leading Power Factor Loads
Blade servers have become a main trend in data centers due to their distinct advantages, such as
higher efficiency, compactness, and ability to increase capacity when needed. These computers
use capacitors at server input to filter out high frequency harmonics produced by the APFC power
supply circuits.
The current in a capacitor has a leading current to voltage characteristic, thus presenting a leading
power factor at the input of the server. Legacy UPS systems are designed to protect inductive
loads which have lagging power factor characteristic. Connecting leading power factor load to UPS
designed to supply only lagging PF load may have a negative affect on UPS capacity, its stability,
longevity, ability to interpret correctly measured data, and the ability to function properly in a
parallel redundant system.
Whereas most single phase UPS systems on the market are still not designed to work with leading
power factor loads, new high power systems are already designed to work both with leading and
lagging power factor loads. Here too however, due to lack of knowledge or awareness, blade
servers are frequently connected to existing or legacy UPS systems, revealing the problem when
system failure occurs.
Conclusion
Matching the right UPS for today and tomorrow requires close acquaintance with existing
infrastructure as well as current and future protection needs. Existing legacy UPS systems on the
site may not work properly with new servers and other future computer loads, designed to meet
latest standards.
Legacy UPS systems from all brands are still actively marketed and promoted by manufactures and
distributors, however procuring the systems which worked fine until now or expanding existing
UPS capacity by adding more legacy systems in parallel with the existing units may not offer the
right protection for new load requirements.
Current situation doesn't allow continuing a conservative approach, implemented in certain
institutions, of divided responsibilities between facility managers responsible for power equipment,
and IT managers in charge of computer servers. Cooperation between these apparently different
functions and proper consultation is required to make sure that new IT equipment can be protected
by current UPS systems, or that procurement of new UPS systems is considered for protection of
new computers.
For more insight on each of the discussed items please see our following articles:
Raising UPS Efficiency with Eco Mode
UPS Inverter Waveform and New Computer Servers
Mind Watts When specifying a UPS
UPS Operation with Blade Server Loads
I welcome remarks. Please send to: meirp@upsonnet.com
UPSonNet Website News
We are constantly updating and adding new items on our existing guides and directories. To update
presented information about your company or products on our product or suppliers' directories or
on UPS manufacturer's directory, please e-mail to denis@upsonnet.com.
To promote your company on UPSonNet website see" Why advertise on UPSonNet"
UPS Industry News
UPSonNet News enable you to see at a glance and become updated about latest UPS industry
news, innovations and trends.
Recent Frost and Sullivan awards to three companies for outstanding performance in the UPS field
might be of particular interest. Riello UPS was granted with 2011 Competitive Strategy Innovation
Award, Legrand was honored for Power UPS differentiation, and Master Power Technologies was
awarded for customer service leadership.
Frost & Sullivan's awards are generally based on users' survey in relation to the specific topic. The
importance of such awards refers not only to the winning company but also to the issues that
users' appreciate, and which every company should strive to meet.
We welcome remarks on any Newsletter issue. Please e-mail to: denis@upsonnet.com
__________________________________________________________________
To receive this newsletter in your e-mail, please subscribe.
Please forward this e-mail to a friend that might be of interest