Three-phase power considerations for racks
Increasing power requirements for racks are making the use of three-phase power at the
rack level compelling.
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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.
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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 flow 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 efficient and less costly installations that require fewer AC cables
and PDUs.
Cable management
Rack installations should be planned for operational efficiency, ease of maintenance, and
safety. Hitachi offers the Backend Configuration Utility (BECK), a graphical, cable-
management application that can relieve the typical cable congestion created when
populating a rack with storage systems and their accessories.
Cable retention
Unintentional unplugging or unseating of a power cable can have a serious impact on
the operation of an enterprise storage system. Unlike data cables, power connectors do
not have built-in retention mechanisms to prevent this from happening.
To prevent accidental unplugging or unseating of power cables, the storage system
includes a rubber cable-retention strap near the AC receptacle on each controller. These
straps, shown in the following image, loop around the neck of a power cable connector,
and the notched tail is slipped over the hook of the restraining bar fixed to the storage
system.
Three-phase power considerations for racks
Appendix F: Data and power cables
Hitachi Virtual Storage Platform G200 Hardware Reference Guide
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