60 I ICT TODAY
Managing capacity
includes how to optimize
and maximize utilization of
the existing capacity and the
ability to plan and forecast
for future needs.
Additional savings can also be achieved by balancing
the power, airflow and pressure increasing ventilation.
There are significant energy savings related
to bringing 415V to the rack. It is estimated that by
using a smaller isolation transfer that goes from 480V
to 415V (in comparison to a larger isolation transformer
which take the incoming voltage of 480V to 208V),
approximately 2 percent in energy losses can be saved.
In addition, when considering IT rack equipment power
supplies, the end user can realize even more efficiencies.
It is estimated that IT equipment switching power supplies
run at approximately 80 percent efficiency at 100V all the
way up to 91 percent11 efficiency at 240V. 415V rack PDU
outlets supply 240V to the attached IT equipment;
the equipment can run as much as 11 percent more
efficiently than the same piece of equipment running
on 120V.
Bringing 415V to the rack is also beneficial as it helps
in lowering infrastructure costs. In reference to the
precious energy savings discussion, using smaller
isolation transformers are not only smaller, but they
are also more cost effective than their larger counterparts
(480V to 208V) per transformer deployed. Next, there
are additional savings that can be achieved in regard
to power cables. Considering what was learned from the
increased power capacity section, a 60A 208V three-phase
rack PDU has equivalent power capacity to a 30A 415V
three-phase rack PDU (i.e., 17,292 VA (60A x .8 x 208V
x 1.732) and 17,250 VA (30A x .8 x 415V x 1.732) accordingly.
The AWG required to carry 30 Amps is 10 AWG
in comparison to the AWG required to carry 60 Amps
which is 6 AWG. Taking a look at the market costs of the
two AWG, there is an approximate savings of $0.28 per
foot. Accordingly, when considering the amount of power
cables that are installed into a data center, these can
provide additional savings to the data center owner.
The cost of outages can be substantial, since it can
damage equipment, cause loss of productivity, loss
of business and in some cases loss of reputation. Outage
risks can be reduced with warning alarms triggered when
overload or potential hot spots are detected. They can
also be reduced by logging power trends for anticipating
overloading, since power has a transient behavior that
needs to be monitored over time to detect and predict
anomalies. Should an outage occur, intelligent rack PDUs
enable the gradual powering-up of the equipment in the
data center avoiding uncontrolled power up that can
create a power surge resulting in continuous outages.
Another benefit is capacity management by finding
best fit and stranded capacity while being able to forecast
remaining capacity and future needs. Low, compact
PDUs help to reduce rack space. Air flow and ventilation
are improved, thereby contributing to reduction
in energy costs.
Quality, reliability, and safety are paramount
considerations when selecting the right intelligent rack
PDU supporting high density power applications. As the
voltages are increased so is the inherent increased risk for
arc flash.
Safety features to look for include 10KAIC (Ampere
Interrupting Capacity) breakers as well as magnetichydraulic
breakers with stable trip characteristics
at extreme temperatures. These breakers provide double
the AIC rating of what would be found in a standard
208V rack PDU which typically has 5 KAIC breakers,
increasing the safety level of the PDU. The AIC rating
indicates the maximum fault current that the breaker
overcurrent protection device will safely clear when
a fault is applied at the load side of the breaker. In
addition, utilizing an IP67 waterproof plug with pin
and sleeve provides secure and reliable connections.
Selecting a 415V PDU provides a great deal of benefits
with regard to capacity and savings in both energy