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P O W E R I N G T E C H N O L O G Y
Manual No. MS0027-MAN rev. 4
guardian_access_3u_ms27-man-rev4-0817.indd
2.3.2.1 Low Voltage Disconnect (LVD) and Dummy LVD
Generally, the system is equipped with low voltage battery disconnection, which prevents
the batteries from deep discharging, thus prolonging the battery life. A disconnection
requires a detected mains failure at the supervision unit.
If disconnection occurs, the batteries will not supply power to the load until they have
been recharged to set voltage level, which can be adjusted by the user.
If disconnection occurs, the batteries will be reconnected when mains supply returns.
A dummy LVD can also be installed into the power system if the Low Voltage
Disconnection function is not needed.
2.3.2.2 Partial Load Disconnection / Load Shedding (PLD)
Partial load disconnection can be configured to be voltage or time dependent, this is
selected when ordering the power system.
At a mains outage the controller will open the PLD contactor when the batteries have
discharged to a certain voltage or if the battery voltage has been under a certain voltage
for a predetermined time. The disconnection has to be set according to the present load
and battery manufacturer’s discharge tables or requirements.
2.3.3 Rectifier Module
The fan-cooled rectifier converts the AC input to -48VDC output for loads and batteries.
It is designed for parallel operation and plug-in installation in the power shelf and supplies
extremely stable DC power.
Each rectifier incorporates an internal microprocessor that sends frequent updates to the
system controller and adjacent rectifiers. This ensures accurately controlled load sharing
among rectifiers and supplies status and identification information to the controller.
The rectifier module features two LEDs for status indication, thermal protection with
power derating, and input over voltage disconnection with automatic reset. The rectifier
module is hot-swappable and can be quickly removed and replaced without disrupting
the system or load.
Handles
Cooling Fans
Status LEDs
Figure 2-5 Guardian Rectifier
