Eaton SC200, Operation Handbook

Page: 44 / 139

SC200 Handbook
36
Copyright © 2007-2011 Eaton Corporation. All Rights Reserved.
IPN 997-00012-50H November 2011
Low Voltage Disconnect (LVD)
Low Voltage Disconnects may be connected either as load disconnect or battery disconnect
depending on the dc power system model. They have two purposes:
to protect a VRLA battery from deep discharge and premature failure, and/or
to reduce the load on a battery under discharge so that high priority equipment operates
for a longer time after an ac supply failure.
The SC200 has 16 independent LVD control channels (LVD 1 to LVD 16). Each channel can
control one or more of up to 16 contactors, with coil voltages from 12V to 48V nominal.

There are two contactor connectors on an IOBGP input/output board. Additional contactors are
controlled by additional IOBGP-01 input/output boards. If required, refer to the dc power system
Installation and Operation Guide for details on how to connect additional IOBGP-01 input/output
boards to the SC200.
LVD Disconnect Modes
The LVD control channels can have any combination of the following modes of operation:
1
Voltage Based Disconnect : The LVD control channel will disconnect its contactor(s) based
on the bus voltage.
2
AC Timer Based Disconnect : The LVD control channel will disconnect its contactor(s) after
a specified period of ac supply failure.
3
Smart Alarm Disconnect : The LVD control channel will disconnect its contactor(s)
according to the state of a specified Smart Alarm . See Smart Alarm Disconnect on page 42 .
If Chained to Previous is enabled, the LVD control channel will only disconnect its contactor(s) if
one of its disconnect conditions is True , and the preceding control channel has been
disconnected for the Recognition Time .

Chained to Previous does not apply to LVD 1.
LVD Default and Custom Configuration
If factory-fitted in the dc power system, the LVD contactors will be characterized and the LVD
control channels will have default configuration settings for
Voltage Based Disconnect . Custom
configuration will only be necessary if:
contactors are connected to the dc power system on site (see LVD Characterization on page
37 and LVD Setup on page 39 )
different disconnect conditions are required (see LVD Configuration on page 41 ).
Typical LVD Arrangements
The simplest use of an LVD is a single battery disconnect contactor.
The following diagram shows a typical arrangement of two LVDs. This arrangement allows
lower priority loads to be disconnected first (contactor controlled by control channel LVD 1),
either at a specified battery voltage or a specified time interval after an ac supply failure. This
then prolongs battery power for the highest priority loads (contactor controlled by control
channel LVD 2). The battery will be disconnected when the battery voltage reaches its
minimum preset voltage.