Download LACCD IT Design Standards

Input Current Limit:
LACCD IT Design Standards 2009
The input converter shall control and limit the input current draw from utility to 130% of the UPS
output. During conditions where input current limit is active, the UPS shall be able to support 100% load,
charge batteries at 10% of the UPS output rating, and provide voltage regulation with mains deviation of
up to +22%/ -10% of the nominal input voltage.
Redundancy: When installing systems in a parallel redundant (PR) configuration, the system shall
include redundant input converters, each with semiconductor fusing, and logic controlled contactors to
remove a failed module from the power bus.
Battery management system: The UPS shall contain a battery management system with the following
features:
Battery Recharge: The battery management system shall provide a three-step charging process. These
periods shall be recognized as constant current, constant voltage and rest. After recharging batteries to
full capacity, UPS shall isolate the charging circuit from the battery. Continual float charging of the
battery shall not be allowed, therefore reducing the possibility of positive grid corrosion, and increasing
expected battery life.
Battery Runtime Monitoring: The battery management system shall monitor battery and provide status
to end user of battery run time via front panel, serial/network communications, or both. Run time
calculations to be based on load demand and analysis of battery health.
Battery Health Monitoring: UPS shall continuously monitor battery health and the UPS will provide
warnings visually, audibly and/or via serial/network communications when battery capacity falls below
80% of original capacity. Battery testing may also be user initiated via the front panel or serial
communications.
Parallel connected systems shall independently monitor their battery voltage during discharge. Each
system shall communicate with other systems on the parallel bus, sending information about current
battery conditions (voltage). Each UPS shall be able to adjust output load based upon its own battery
voltage, therefore systems with incorrectly connected, weak or failed batteries shall assume less load
ensuring maximum runtime out of the connected battery. Adjusting output loading based on battery
voltage shall not allow a UPS inverter to exceed more than 100% of its rated capacity.
The battery charging circuit shall remain active when in any normal mode of operation or while in static
bypass mode.
Back-feed Protection: Each UPS shall provide a UL1778 approved back-feed protection scheme.
Enterprise Data Center Design – Std 003-0909
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