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5.5 Uninterruptible Power Supply (UPS)
(1) Selection of UPS
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Use of a UPS is recommended to minimize power outages or momentary voltage drops (flickers) of
commercial power due to lightning strikes.
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Select a power supply such as a line interactive UPS so that the momentary voltage drop that occurs when
switching to battery operation does not fall below the flicker tolerance(10ms) of the disk array unit.
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Installing a UPS for each redundant power supply of the disk array unit is recommended to limit the effect of
a UPS equipment failure.
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If one unit of a redundant power supply fails, the total power load is supplied from the other power supply.
Therefore, the total power load must be able to be supplied even if the UPS electric power selection is
supplied to one unit of a redundant power supply.
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Select a UPS that satisfies the requirements for both the total apparent power (VA) and the total effective
power (W) of the disk array unit.
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Since the starting current (inrush current) of the disk array unit flows to the UPS, select a UPS that permits
this current.
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The disk array unit is equipped with switching power supplies and an X/Y capacitor to counter EMI at its input.
When numerous devices are connected to the UPS, the leading phase current due to the capacitor increases.
Since a large oscillating current may occur in some UPS devices due to this leading phase current causing the
circuit breaker between the UPS and disk array unit to burnout, check with the UPS manufacturer to make
sure that this will not be a problem. Note that this has been verified for UPS devices manufactured by NEC
and NEC Fielding.
(2) Setup
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For a UPS that allows the power fault detection sensitivity to be switched and the permissible voltage to be
set, use manual switches and automatic running software such as EMSPRO/AC Enterprise to set the
recommended sensitivity (high sensitivity) and recommended voltage according to the UPS and automatic
running software user's guides.
・
If a UPS is installed for each redundant power supply of the disk array unit, set each UPS so that both
devices will be on almost simultaneously (within one minute). If the times in which the two UPS devices
are on differ significantly, a power fault may be detected in the disk array unit.
Warning
