Eaton SC100 - Page 34

SC100 Handbook
28
Copyright © 2008-2011 Eaton Corporation. All Rights Reserved.
IPN 997-00012-63C August 2011
The SC100 has two LVD control channels (LVD1 and LVD2) with three modes of operation:
1 Normal Mode: In this mode LVD2 Slave Mode and AC Timer Mode are disabled, and LVD2
(if Enabled) will only disconnect after LVD1.
2 LVD2 Slave Mode: In this mode LVD2 has the same operating parameters as LVD1.
3 AC Timer Mode: The LVD will disconnect either after the AC Timer Disconnect Delay, or
the bus voltage drops to the Disconnect Voltage, whichever happens first. Both LVD1 and
LVD2 can be set to AC Timer mode if required (but LVD2 will only disconnect after LVD1).
The following diagram shows a typical two LVD configuration. This allows lower priority loads
to be disconnected first (LVD1), 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
(LVD2). The battery will be disconnected when the battery voltage reaches its minimum preset
voltage.

LVD1 - low priority load
disconnect (disconnects
first).

LVD2 - battery disconnect
(only disconnects after
LVD1)

Connections to high
priority loads (for example
transmission equipment).

Connections to low
priority loads.

Connection to the SC100
system controller via the
I/O board.
Characterization
If auxiliary contacts are fitted to the LVD contactor(s)*, then the LVD Characterization process
determines the optimum operating voltages to suit the contactor(s) coil voltage. These values
are stored in the SC100 and on the I/O board.
An LVD Characterization Error alarm will be activated if the SC100 detects that the
characterization values stored in the SC100 and on the I/O board are different. This happens
when:
 The SC100 is replaced. To clear the alarm, on the SC100 select Use IOB Values.
 The I/O Board is replaced. To clear the alarm, on the SC100 select Use SC Values.
 Both the SC100 and the I/O Board are replaced. In this case, re-characterize the
contactor(s).
 When a contactor is re-characterized it will disconnect and re-connect several times. Refer to
Maintenance in the dc power system Installation and Operation Guide for full instructions.