Evaluating the Opportunity for DC Power in the Data Center - by Mark Murrill and B.J. Sonnenberg, Emerson Network Power

Page created by Erica Reid
 
CONTINUE READING
Evaluating the Opportunity for DC Power in the Data Center - by Mark Murrill and B.J. Sonnenberg, Emerson Network Power
A White Paper from the Experts
                                                             in Business-Critical Continuity™

Evaluating the Opportunity for DC Power in the Data Center
by Mark Murrill and B.J. Sonnenberg, Emerson Network Power
Summary

With data center managers struggling to increase efficiency while maintaining or
improving availability, every system in the data center is being evaluated in terms of its
impact on these two critical requirements. The power system has proven to be one of
the more difficult systems to optimize because efficiency and availability are often in
conflict; the most efficient approach to critical power is rarely the most reliable.

One solution to power system optimization that deserves serious consideration is DC
power. Since utility AC power must ultimately be converted to DC for use by IT system
components and because stored energy systems (batteries, flywheel, etc.) provide DC
power for backup, a DC power architecture requires fewer total conversions from grid to
chip, creating the opportunity to reduce costs and increase efficiency.

A data center-optimized, row-based DC power protection system is now available to help
data center operators take advantage of that opportunity. This system, combined with
the availability of 48V DC-powered IT equipment from major manufacturers, makes DC
power an ideal solution for small and midsize data centers seeking to optimize efficiency,
reliability and scalability. Other applications include high-density equipment rows with a
consistent footprint and pod-based data centers.

As the leading provider of AC and DC power systems, Emerson Network Power is uniquely
positioned to help organizations evaluate the suitability of DC power and determine
whether a row-based DC infrastructure is appropriate for a given application.

                                                                                             2
Introduction
The first decade of the twenty-first                      concerns among data center managers as                The industry responded with a new
century was one of incredible growth                      they struggled to adapt to a 400 to 1,000             focus on energy efficiency and began
and change for data centers. The demand                   percent increase in rack density.                     implementing server virtualization, higher-
for computing and storage capacity                                                                              efficiency server power supplies, and new
                                                          The dramatic increase in data center
exploded, and many IT organizations                                                                             approaches to cooling. Yet, while signifi-
                                                          energy consumption created both financial
struggled to deploy servers fast enough                                                                         cant progress has been made in some
                                                          and environmental challenges. Energy
to meet the needs of their businesses. At                                                                       areas, the critical power system has yet to
                                                          costs, which once had been relatively
the same time, the trend to consolidate                                                                         be fully optimized. While individual com-
                                                          inconsequential to overall IT management,
data centers and centralize computing                                                                           ponents have been improved, the overall
                                                          became more significant as the rise in
resources resulted in fewer opportunities                                                                       system complexity is high, which can
                                                          consumption was exacerbated by a
for planned downtime while also increas-                                                                        create inefficiency and add operational
                                                          steady—and in some years significant—
ing the cost of unplanned outages.                                                                              risk. Faced with the choice of increasing
                                                          increase in the cost of electricity. In
                                                                                                                system efficiency or adding risk, many
Data center operators were able to meet                   addition, increased awareness of the role
                                                                                                                continue to choose proven approaches
the demand for increased compute                          that power generation plays in atmospheric
                                                                                                                that deliver high availability but do not
capacity by deploying more powerful                       carbon dioxide levels prompted the U.S.
                                                                                                                deliver the highest efficiency.
servers—often in the same physical space                  EPA to investigate large energy consumers
as the servers being displaced—creating a                 such as data centers. In 2007 the EPA                 However, a close examination of the
dramatic rise in data center power con-                   presented a report to the U.S. Congress that          available options reveals that, in many
sumption and density. Between 2004 and                    included recommendations for reducing                 cases, efficiency can be improved without
2009, power and heat density became top                   data center energy consumption.                       sacrificing overall availability.

Established Data Center Power Distribution Options
Traditional AC power distribution systems in North America bring 480V AC power
into a UPS, where it is converted to DC to charge batteries, and then inverted back
to AC. The power is then stepped down to 208V within the distribution system (PDU) for
delivery to the IT equipment. The power supplies in the IT equipment convert the power
back to DC and step it down to lower voltages that are consumed by processors, memory
and storage [Figure 1].

                           Double Conversion UPS                                                                                     Server
                                     Bypass
                                                                                                PDU                           PSU

    480V AC                                                               480V AC                          208V AC      AC        DC     12V DC
                       Rectifier              Inverter                                       Transformer                                          Load
                                                                                                                             DC     DC

                                    Battery

Figure 1.1.
Figure    Typical 480V480V
            Typical    AC to 208V
                             AC toAC208V
                                     data center power
                                           AC data     systempower
                                                    center    configuration.
                                                                     system configuration.

3                          Double Conversion UPS                                                                                     Server
                                     Bypass
                                                                                                PDU                           PSU
In recent years, manufacturers have                             In the event of a power interruption, a                    First, by connecting loads phase-to-neutral,
increased component efficiencies and                            switching function is required to bring the                additional harmonic currents may be intro-
developed new operating modes, such                             load back on to the inverter, and mains                    duced, offsetting some of the anticipated
as the “eco-mode” available on some UPS                         need to be quickly isolated to prevent                     efficiency gains. Second, because of the
systems, to improve efficiency.                                 power feedback into the distribution                       elevated voltages at the rack, arc flash
                                                                system. No matter how fast or reliably                     concerns for IT personnel working in the
Figure 2 shows AC UPS operation when
                                                                this switching occurs, there is still a chance             rack will increase. Finally, there are no
in eco-mode. Efficiency is improved by
                                                                it will fail when it is needed most.                       commercially available power supplies at
bypassing the conversion in the inverter;
                                                                                                                           this input level. All in all, this architecture
however, this introduces the potential for                      There has been discussion in the industry
                                                                                                                           needs further development before it can
reduced system reliability. Critical loads                      about simplifying the AC distribution
                                                                                                                           be considered a true alternative.
are no longer isolated from the mains or                        scheme by eliminating the step-down in the
subject to the tight voltage regulation                         power distribution unit and delivering higher           Consequently, 48V DC power may prove to
                       Double
                       Double  Conversion
                               Conversion  UPS                                                                                                Server
normally provided by the   inverter,  and UPS                   voltages to the IT equipment. One exam-                                       Server
                                                                                                                        be the best alternative  to 480V/208V AC
complex synchronization circuits are
                             Bypass
                             Bypass                             ple, illustrated in Figure 3, takes 277V AC             power distribution for organizations seeking
                                                                                                  PDU
                                                                                                  PDU                                 PSU
                                                                                                                                      PSU
needed to ensure reliable power transfer.                       output from the UPS and delivers      it directly       to optimize reliability and efficiency today.
   480V
   480V AC
        AC              Rectifier                 Inverter
                                                                to the server power
                                                                               480V AC
                                                                               480V AC supply. This  approach     208V AC
                                                                                                                  208V AC        AC
                                                                                                                                 AC      DC
                                                                                                                                         DC       12V
                                                                                                                                                  12V DC
                                                                                                                                                      DC    Load
                        Rectifier                 Inverter                                    Transformer
                                                                                              Transformer                                                   Load
                                                                                                                                    DC
                                                                                                                                    DC     DC
                                                                                                                                           DC
                                                                may have potential in the future but is not
                                                                viable today for a number of reasons.
                                       Battery
                                       Battery

Figure
Figure 1.
       1. Typical
          Typical 480V
                  480V AC
                       AC to
                          to 208V
                             208V AC
                                  AC data
                                     data center
                                          center power
                                                 power system
                                                       system configuration.
                                                              configuration.

                            Double
                            Double Conversion
                                   Conversion UPS
                                              UPS                                                                                                Server
                                                                                                                                                 Server
                                       Bypass
                                       Bypass
                                                                                                    PDU
                                                                                                    PDU                                   PSU
                                                                                                                                          PSU

   480V AC
   480V AC                                                                       480V AC
                                                                                 480V AC                              208V AC
                                                                                                                      208V AC       AC
                                                                                                                                    AC        DC
                                                                                                                                              DC     12V DC
                                                                                                                                                     12V DC
                        Rectifier
                        Rectifier                    Inverter
                                                     Inverter                                   Transformer
                                                                                                Transformer                                                    Load
                                                                                                                                                               Load
                                                                                                                                         DC
                                                                                                                                         DC     DC
                                                                                                                                                DC

                                       Battery
                                       Battery

 Figure
 Figure 2.
        2.2.In eco-mode, incoming power
                                  power bypasses
Figure     InIneco-mode, incoming
                 eco-mode,    incoming   powerthe
                                        bypasses the inverter
                                                     inverter to
                                                  bypasses    to increase
                                                                 increase
                                                               the        UPS
                                                                          UPS system
                                                                    inverter  system efficiency.
                                                                                     efficiency.
                                                                              to increase    UPS system efficiency.

                            Double Conversion
                            Double Conversion UPS
                                              UPS                                                                                                Server
                                                                                                                                                 Server
                                       Bypass
                                       Bypass
                                                                                                    PDU
                                                                                                    PDU                                   PSU
                                                                                                                                          PSU

   480V AC
   480V AC                                                                     480V/277V AC
                                                                               480V/277V AC                           277V AC
                                                                                                                      277V AC       AC
                                                                                                                                    AC        DC
                                                                                                                                              DC     12V DC
                                                                                                                                                     12V DC
                        Rectifier
                        Rectifier                 Inverter
                                                  Inverter                                                                                                     Load
                                                                                                                                                               Load
                                                                                                                                         DC
                                                                                                                                         DC     DC
                                                                                                                                                DC

                                       Battery
                                       Battery

Figure
 Figure 3.3.480V
 Figure 3.   480V
           480V  AC AC277V
                 AC to
                    to  to 277V
                       277V    dataAC
                            AC data
                            AC        data
                                    center
                                    center   center
                                           power
                                           power     power
                                                 system
                                                 system      system configuration.
                                                        configuration.
                                                        configuration.

                                                                                              Switch
                                                                                              Switch                                                                    4

                                                                                       PSU
                                                                                       PSU
                                                      PDU
                                                      PDU
480V AC              Rectifier                 Inverter                       480V AC           Transformer             208V AC      AC        DC     12V DC   Load
                         Rectifier                 Inverter                                         Transformer                               DC     DC            Load
                                                                                                                                              DC     DC

                                         Battery
                                         Battery

Figure 1. Typical 480V AC to 208V AC data center power system configuration.
Figure 1. Typical 480V AC to 208V AC data center power system configuration.

                 Double      Double Conversion UPS                                                                                                    Server
A Practical Approach  toConversion
                         DC in the UPSData Center                                                                                                     Server
                                          Bypass
                                          Bypass                                                     PDU                                  PSU
Historical Background                                           Today, telephone central offices     PDU                  -48V power supplies
                                                                                                                                          PSU     at the point of use. The
48V   DC
   480V ACpower has a long history in tele-                     (exchanges) are  480Vstill
                                                                                      AC powered by -48V DC. 208V AC      power supplies
                                                                                                                                     AC     step
                                                                                                                                             DC the voltage
                                                                                                                                                       12V DC down to
   480V AC               Rectifier                   Inverter                    480V AC         Transformer        208V AC          AC      DC        12V DC     Load
                         Rectifier                   Inverter These facilities exhibit levels      of  availability
                                                                                                 Transformer              12V   and lower
                                                                                                                                        DC DC voltages
                                                                                                                                               DC         for internal
                                                                                                                                                                  Load uses.
communication networks. It is inherently                                                                                                DC     DC
simple and reliable with few conversion                         as high  as  9-nines,    as confirmed   in a study
                                                                                                                          It is easy to see the benefits of this
                                        Battery                 of 23,000 DC power systems over 10 years
stages to the point of use. In AlexanderBattery
                                                                                                                          approach when applied to the data center.
Graham Bell’s day, 48V DC was chosen as                         by NTT Facilities1.
                                                                                                                          Downstream of the AC/DC rectifiers, the
the  standard     for two  reasons:                             In most  telecommunications
Figure 2. In eco-mode, incoming power bypasses the inverter to increase UPS system efficiency.    installations, the      power is completely isolated from the
Figure 2. In eco-mode, incoming power bypasses the inverter to increase UPS system efficiency.
  1. DC power was felt to be more reliable                      48V DC power system is deployed as three                  mains and is considered “safety extra low
      than AC because it could be directly                      distinct elements as shown in Figure 4:                   voltage” (SELV) per IEC/UL 60950 and can
      connected to backup   Double  batteries  during             1. 480V AC to -48V DC modular                           be maintained live by trained personnel.
                            Double Conversion
                                       Conversion UPSUPS                                                                                          Server
                                                                                                                                                  Server
      grid outages;                                                   power system                                        In addition, there is no   need to derate
                                        Bypass                                                                            capacity to account     for phase balancing or
  2. 48V was considered the optimal     Bypass
                                                                  2. Battery banks for extended      PDUrun time
                                                                                                     PDU
                                                                                                                                          PSU
                                                                                                                                          PSU
      tradeoff between transmission                                                                                       harmonics,     which  are not a factor with DC
   480V AC                                                            (at least  8 hours)
                                                                              480V/277V   AC                        277V AC          AC      DCsafety 12V  DC
   480V AC
      distance and human Rectifier
                         Rectifier safety because
                                                 Inverter
                                                 Inverter
                                                                              480V/277V   AC                        277V  power.
                                                                                                                         AC        Personnel
                                                                                                                                     AC      DC        is also
                                                                                                                                                       12V DC improved
                                                                                                                                                                  Load
                                                                                                                                                                  Load
                                                                                                                                        DC     DC
                                                                  3. Load distribution cabinets (BDFB/PDU)                when          DC
                                                                                                                                  servicing    DC
                                                                                                                                             equipment     in the rack
      it is considered safe to touch during
      maintenance or accidentalBattery   exposure.              These elements are connected with large                   because arc flash is not a concern at -48V.
                                         Battery
                                                                copper bus bars and wires routed around                          However, unlike telecommunications cen-
                                                                the facility to distribute power directly to                     tral offices, data centers are not designed
Figure 3. 480V AC to 277V AC data center power system configuration.
Figure 3. 480V AC to 277V AC data center power system configuration.                                                             with large copper bus bars to distribute
                                                                                                                                 DC power to racks. Fortunately, with new
                                                                                                                                 row-based DC topologies, these large
                                                                                                 Switch
                                                                                                 Switch                          copper runs are no longer necessary. In
                                                                                                                                 this row-based configuration, power is
                                                                                          PSU
                                                        PDU                               PSU                                    converted from AC to DC very close to
                                                        PDU
    480V AC         Rectifiers       48V DC                            48V DC           DC         12V DC                        the point of use, which decreases the
    480V AC         Rectifiers       48V DC                            48V DC           DC         12V DC      Load
                     (N+m)                                                                DC                   Load
                     (N+m)                                                                DC                                     conductor size and cost [see Figure 5].

                                     Battery                                                                                     Data centers are entering a new stage of
                                     Battery
                                                                                                                                 maturity where the emphasis is on reliably
                                                                                                                                 delivering more computing capacity to
 Figure 4.4.-48VDC
Figure        -48V power as typically
                   DC power           implemented
                                as typically      in telecommunications
                                              implemented               central offices.
                                                              in telecommunications      central offices.                        the organization at lower cost and with
 Figure 4. -48VDC  power as typically implemented in telecommunications central offices.
                                                                                                                                 reduced power consumption. Row-based
                                                                                                                                 DC power represents a practical and
                                 Row-Based
                                 Row-Based DC
                                           DC UPS
                                              UPS                                                Server
                                                                                                 Server                          affordable solution for reducing data
                                                                                                                                 center complexity, increasing efficiency
                                                                                          PSU
                                                                                          PSU                                    and enabling growth.
    480V AC                Rectifiers                                 48V DC            DC         12V DC
    480V AC                Rectifiers               PDU               48V DC            DC         12V DC      Load
                            (N+m)                   PDU                                   DC                   Load
                            (N+m)                                                         DC

                                         Battery
                                         Battery

Figure 5. A row-based DC UPS minimizes the amount of copper and floor space required for installation in the data center.
Figure 5. A row-based DC UPS minimizes the amount of copper and floor space required for installation in the data center.
Figure 5. A row-based DC UPS eliminates the long copper runs and is optimized for the data center.

5
Factors Affecting Power Distribution Selection
When selecting an optimal power architec-          Intel concluded that DC power (both 400V and 48V) was
ture for a particular facility, the number
of factors data center designers and
                                                   consistently more efficient than AC at all voltages.
managers have to consider is substantial.
Understanding the impact of each factor            While each study created scenarios that        Power offers an efficiency-optimizing
is essential to making an informed choice          allowed for direct comparison of different     feature that maintains near-peak effi-
for your data center.                              configurations, many aspects of the power      ciencies at system loads as low as 5%,
                                                   distribution system are complex and vary       allowing the system to achieve both
Efficiency
                                                   by application, making general compari-        high availability and efficiency in real
End-to-end power system efficiency                 sons difficult. Aspects which were not         world conditions.
can be difficult and time consuming to             considered in either study include the         Harmonics
accurately calculate due to the complexity         degree of desired redundancy, the impact       Harmonics are a distortion of the
of variables involved, but it is still useful to   of harmonics and load variations, and the      normal AC waveform generally trans-
consider and approximate efficiency based          added load on cooling created by inefficient   mitted by non-linear loads. In the
on specific site conditions and priorities.        systems. In cases where these factors are      data center, the switch-mode power
In light of recent improvements in the             present, the gaps between DC and AC            supplies used in AC servers represent
efficiency of both AC and DC architectures,        would likely be wider, as the following        a non-linear load that can create
two vendor-neutral studies have been               analysis reveals.                              harmonics. Harmonic currents accu-
published by The Green Grid and Intel                  Redundancy                                 mulate in the neutral wire, causing
to provide an objective, yet simplified,               The degree of redundancy in the            distribution losses and increased heat
comparison of the efficiency of various                power distribution system can              generation. If the cumulative level of
power system configurations.                           impact both availability and               harmonics—known as total harmonic
The results from The Green Grid’s study,               efficiency. In the case of AC power        distortion—becomes too high, damage
“Quantitative Efficiency Analysis of Power             distribution, these two factors may        to sensitive electronics and reduced
Distribution Configurations for Data                   be mutually exclusive—greater              efficiency can result and may require
Centers”2, for the power architectures                 redundancy increases availability          equipment derating to overcome.
discussed here, evaluated at 50 percent                but lowers overall efficiency.             These losses are difficult to predict in
operating load, are summarized below:                                                             complex AC distribution systems, but
                                                       The highest availability is achieved
                                                                                                  could be quite significant. Harmonics
     480V AC to 208V AC (legacy):                      through 2N redundancy in which
                                                                                                  are not present in DC systems because
     63 percent efficient [Figure 1]                   each UPS module is designed to run
                                                                                                  there are no waveforms to contend with.
                                                       at no more than 50 percent load.
     480V AC to 208V AC (current):
                                                       However, since the data center is          Data Center Load Variations
     88 percent efficient [Figure 1]
                                                       rarely operating at peak capacities,       Many data centers are operating at
     480V AC to 277V AC:                                                                          significantly less than 100 percent of
                                                       the redundant systems are almost
     89 percent efficient [Figure 3]                                                              design load much of the time, with
                                                       always operating at less than 50
     480V AC to 48V DC:                                percent capacity. With derating,           real-time loads changing frequently.
     90 percent efficient [Figures 4 & 5]              maximum capacity may be closer to          This variation further complicates
                                                       40 percent, and, in normal operation,      efficiency modeling. As servers are
Intel conducted a similar analysis,
                                                       each unit may operate at 20 percent        turned on/off and utilized at different
“Evaluation of 400V DC Distribution in
                                                       load or less. Most equipment               rates, the loading on each phase of
Telco and Data Centers to Improve Energy
                                                       efficiency curves drop dramatically        a 3-phase power system changes,
Efficiency”3 and found that the highest
                                                       below 30 percent load, resulting in        making alignment between the three
overall system efficiencies are achieved
                                                       actual operating efficiencies signifi-     phases difficult. Unbalanced loads
with a 400V DC system; however, this tech-
                                                       cantly less than ideal conditions.         lower total system efficiency and
nology is not yet commercially available.
                                                                                                  produce additional heat.
Overall, this study concluded that DC                  In the case of DC power, redundancy
power (both 400V and 48V) was consis-                  can be seamlessly integrated into the
tently more efficient than AC at all voltages.         DC UPS. In addition, Emerson Network
                                                                                                                                         6
In the white paper “Phase Balancing:       Availability                                       With a complete data center power and
    The Last Few Inches of a High-             Both AC and DC power systems can be                cooling infrastructure integrated into a fully
    Efficiency Power System”4, Server          designed to achieve high availability. The         enclosed container, these systems can be
    Technology analyzes the impact of          highest availability facilities will likely con-   delivered to a site and quickly plugged into
    unbalanced loads on a 30A, 240/415V        tinue to use 2N redundancy because of its          power, communications and chilled water
    3-phase circuit loaded in a Wye            ability to support a dual-bus architecture         systems to enable additional computing
    configuration. If the load is balanced,    that can eliminate downtime from system            capacity. With its built-in redundancy and
    the current through each input phase       failures across the entire power distribution      compact footprint, a DC UPS is an excellent
    is 8A, and losses can be calculated at     chain. However, that availability comes            solution for these applications.
    19 watts per 100 feet of cable. In         with a cost, both in terms of upfront
                                                                                                  This same philosophy is also manifesting
    the most unbalanced case, current          equipment and ongoing operating
                                                                                                  itself in the move toward row-based equip-
    through one phase is 24A and losses        efficiencies. Many organizations can
                                                                                                  ment, which enables modular expansion
    escalate to 115 watts per 100 feet of      achieve desired levels of availability from
                                                                                                  of existing facilities or support for high
    cable. This shows that power loss and      N +1 redundancy in which redundancy is
                                                                                                  density rows. Both AC and DC UPS systems
    heat generated in feeder cables can        maintained at the module level.
                                                                                                  provide scalability in a row-based format,
    increase by as much as 600 percent
                                               At the system level, there are two ways that       but the DC UPS has the benefit of built-in
    because of unbalanced loads.
                                               DC power systems offer high availability.          redundancy and will occupy at least 50
    Additionally, keeping track of which
                                               First, the DC power conversion system has          percent less floor space than a comparable
    base loads are on which phase can be
                                               fewer components than a comparable AC              row-based AC system.
    time consuming and tedious depend-
    ing on the sophistication of the site      system, which contributes to a higher
                                                                                                  Cost
    and the tools available. Load balancing    mean time between failure (MTBF) rate and
                                               more uptime. In addition, the DC UPS uses          The main purpose of the critical power
    issues are also specific to three-phase
                                               an array of discrete rectifiers to deliver con-    system is to eliminate power-related
    AC power and are not a concern
                                               ditioned, isolated power to a distribution         downtime; any cost comparison should
    with DC.
                                               bus. These rectifiers provide built-in redun-      consider the level of availability required
    Power-Related Heat Loads                                                                      and the cost of downtime. In general, row-
                                               dancy; the system can accommodate the
    After the IT equipment itself, the cool-                                                      based DC power applications will be less
                                               failure of any individual rectifier without
    ing system is the next largest user of                                                        expensive to install, operate and maintain
                                               immediately affecting performance or
    power in the data center. Not only is                                                         than a comparable AC system and will
                                               capacity. Individual rectifiers can be safely
    cooling required for the heat gener-                                                          support redundancy levels of at least N + 1.
                                               hot-swapped out in the field without
    ated from the IT equipment, but it                                                            Some savings may be offset by increased IT
                                               impacting system operation, thus minimiz-
    also must offset the heat generated                                                           equipment costs in a DC system—list prices
                                               ing system mean-time-to-repair (MTTR),
    by power conversion losses. With                                                              for servers with DC power supplies can be
                                               a major contributor to unavailability.
    fewer required conversions and                                                                up to 10 percent higher than the more
    greater overall efficiencies, a DC         Scalability                                        common AC servers. These costs may be
    power system generates less heat           With equipment and rack density rising             negotiable and should come down with
    than an AC system, reducing data           steadily, the power system can become a            the higher volumes that accompany
    center cooling energy consumption.         constraint to growth. As a result, modular         increased adoption. Overall, a DC-based
    As a rule of thumb, each watt of heat      approaches to data center design and               end-to-end power architecture can be as
    generation removed from the data           expansion are gaining in popularity as             much as 30 percent less expensive than
    center leads to an additional 1.4 to 2     demonstrated by the trend toward                   an AC system, depending on many of the
    watts saved in cooling.                    “containerized” data centers.                      factors above.

7
NetSure™ ITM Row-Based DC UPS
The NetSure™ ITM is a data center-optimized
row-based 48V DC UPS from Emerson
Network Power. It is designed to support
the move to higher efficiency, density
and flexibility enabled by row-based
power and cooling. Instead of deploying
one large DC power plant, which would
require DC power to be distributed across
the facility, 480V AC power is delivered
directly to the NetSure™ ITM, which then
provides protected power to racks of 48V
equipment in close proximity [Figure 6].
When additional racks of IT and commu-
nications equipment are required for data
center growth, new DC UPS units can be
added without disruption.

The NetSure™ ITM integrates power
conversion, battery backup and branch
distribution into a compact, highly reliable    Figure 6. The NetSure™ ITM is positioned within the row to provide power to multiple racks.
power protection system. (12) individual
AC/DC power conversion units (PCUs)
deliver 70kW per module of conditioned,
isolated 48V power to an internal distribu-     This DC UPS comes pre-assembled and
tion bus that charges the batteries and         factory tested to simplify installation. The
distributes power directly to the IT or com-    only field connections required are the AC
munications equipment. Backup time is           input to the module and the output to DC
5-10 minutes at full load with the included     loads. In addition, individual components
10 year-VRLA batteries; traditional DC          are user replaceable and can be swapped
systems may be more appropriate if more         out while the system is operating, allowing
than 60 minutes of backup is required.          live maintenance without bypass or
                                                generator switchover.
The system provides up to 22 branch
circuits protected by 100A to 200A circuit      The NetSure™ ITM features an integrated
breakers. Each branch is monitored in the       control and monitoring system that pro-
controller for load and trip condition and is   vides data on input and output parameters
designed to support varying rack densities.     (including branch circuit loads), as well
Power distribution in the rack is provided      as advanced Albér battery management.
by NetSure™ RDB Series zero-U distribution      An Energy Optimization Mode featuring               Figure 7. A zero-U power
                                                                                                    distribution unit provides
units that feature plug-and-play connectors     Intelligent Power Matching ensures near-
                                                                                                    power to 48V input loads.
for easy installation and tool-less             peak efficiency for loads down to 5 percent
maintenance [Figure 7].

                                                                                                                                              8
Conclusion                                       References
by keeping a minimum number of PCUs           Direct current is already a fundamental          [1] “Reliability Field Data of
near full load and putting the rest on        part of your IT infrastructure: critical loads       Power Systems.” NTT Facilities.
standby with the ability to respond quickly   consume DC power and all backup sources              INTELEC 2007.
to changing load conditions.                  generate it. Furthermore, the electric grid      [2] “Quantitative Efficiency Analysis of
                                              distributes AC power. So, the question               Power Distribution Configurations for
Because it eliminates the need for large
                                              becomes, where is the optimal point at               Data Centers.” The Green Grid. 2008.
copper runs and offers the reliability and
                                              which to convert AC to DC power while
scalability inherent in DC power, the                                                          [3] Pratt, Annabelle et al. “Evaluation of
                                              providing suitable protection from outages?
NetSure™ ITM is ideal for a variety of                                                             400 VDC Distribution in Telco and
                                              If the conversion occurs too early,
data center applications, including:                                                               Data Centers to Improve Energy
                                              DC power must be transported long
    Sites with an existing constrained        distances, which requires large conductors           Efficiency.” Intel. 2007.
    power infrastructure or problems          to reduce losses. If it occurs too late, addi-   [4] “Phase Balancing: The Last Few Inches
    with harmonics                            tional conversions are introduced into the           of a High-Efficiency Power System.”
    Data centers seeking to optimize          process which may compromise efficiency              Server Technology. 2010.
    efficiency and availability while         and reliability and increase costs.
    establishing a path for growth by
                                              In many applications, the ideal point for
    using DC power in concert with
                                              power conversion and energy storage is as
    existing AC systems
                                              close as possible to the load. A row-based,
    Modular or pre-configured data            48V DC UPS allows for optimal efficiency,
    center layouts                            reliability and flexibility in these data
    High-density scalable blade deployments   center environments.

                                              The NetSure™ ITM from Emerson Network
                                              Power, combined with the availability of
                                              DC-powered IT equipment from major
                                              manufacturers, makes 48V DC power a
                                              practical, efficient and cost-effective
                                              solution for managing the conversion
                                              from AC grid power to DC power required
                                              by IT equipment.

                                              The simplicity, efficiency and reliability
                                              inherent in the NetSure™ ITM system can
                                              reduce complexity and costs in a variety
                                              of applications and should be seriously
                                              considered for mid-size data centers and
                                              facilities with increasing capacity needs.

9
Emerson (NYSE:EMR), based in St. Louis, Missouri (USA), is a global leader in bringing technology and engineering
together to provide innovative solutions for customers in industrial, commercial, and consumer markets through its
network power, process management, industrial automation, climate technologies, and appliance and tools businesses.
For more information, visit: Emerson.com.

Emerson Network Power, a business of Emerson (NYSE:EMR), is the global leader in enabling Business-Critical Continuity™
from grid to chip for telecommunication networks, data centers, health care and industrial facilities. Emerson Network
Power provides innovative solutions and expertise in areas including AC and DC power, precision cooling, embedded
computing and power, integrated racks and enclosures, power switching and controls, infrastructure management,
and connectivity. All solutions are supported globally by local Emerson Network Power service technicians. For more
information on Emerson Network Power’s full suite of solutions specifically supporting the communications network
infrastructure, visit: EmersonNetworkPower.com/EnergySystems.

Learn more about the NetSure™ ITM DC UPS from Emerson at: EmersonNetworkPower.com/NetSureITM.

This publication is issued to provide outline information only which (unless agreed by Emerson Network Power Energy Systems, North America, Inc. in writing) may not be
used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. Emerson
Network Power Energy Systems, North America, Inc. reserves the right to alter without notice the specification, design or conditions of supply of any product or service.

Emerson®, Emerson Network Power™, Business-Critical Continuity™ and NetSure™ are trademarks of Emerson Electric Co. and/or one of its subsidiaries.

Additionally, this brochure references the following company trademarks: NTT Facilities, The Green Grid, Intel and Server Technologies. Names of companies and products
are trademarks or registered trademarks of the respective companies. Any questions regarding usage of trademark names should be directed to the original manufacturer.

Emerson Network Power
Energy Systems, North America
4350 Weaver Parkway, Warrenville, IL 60555
Toll Free: 800-800-1280 (USA and Canada)
Telephone: 440-246-6999 Fax: 440-246-4876
Web: EmersonNetworkPower.com/EnergySystems

Emerson Network Power.
The global leader in enabling Business-Critical Continuity™.                                                                       EmersonNetworkPower.com
    AC Power                    Embedded Computing                                         Outside Plant                                 Racks & Integrated Cabinets
    Connectivity                Embedded Power                                             Power Switching & Controls                    Services
    DC Power                    Infrastructure Management & Monitoring                     Precision Cooling                             Surge Protection

© 2010 Emerson Network Power Energy Systems, North America, Inc. All rights reserved.
Code: 124W-DCDATA / 1010
You can also read