These requirements must be added to the power demands of any other electrical
de
vices installed in the rack to arrive at a total power consumption gure. In addition,
surge currents must be accommodated. Disk drives normally consume twice the amount
of current at startup as they do during steady-state operation.
Power considerations
Hitachi storage systems have an input power rating of 125V–200V operation. The units
come with a set of power cables.
Note: The po
wer cables included with the storage system are considered part
of the unit and are not intended for use with any other equipment.
A label near the power cord indicates the correct voltage, frequency, current draw, and
power dissipation that should be used with the cable. Please be sure to use the
appropriate power cable for your location. Also, check the power at your site to verify
that you are receiving “clean” power (free of spikes and noise). Install a power conditioner
if necessary.
Three-phase power considerations for racks
Increasing power requirements for racks are making the use of three-phase power at the
rack level compelling.
■
With single-phase power, at any given time the voltage across the hot and neutral
conductors can be anywhere between its peak (maximum) and zero. Electrical
conductors must be large to meet high amperage requirements.
■
Three-phase power uses three cycles that are 120 degrees out of phase, which never
allows the voltage to drop to zero. The more consistent voltage derived from the
three hot conductors results in smoother current ow and allows small-gauge
conductors to be used to distribute the same amount of AC power. As a result, the
load balancing and increased power handling capabilities of three-phase distribution
can result in more ecient and less costly installations that require fewer AC cables
and PDUs.
Sources of electrical interference
V
erify that the storage system is protected from sources of electrical interference.
The following table provides examples of electrical interference.
Power considerations
Chapter 2: Power requirements
Site Preparation Guide for VSP G/F350, G/F370, G/F700, G/F900 47
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