Vertiv™ | Liebert
®
STS2
™
100-1000A, 50/60Hz User Manual | Rev. 12 | 11/2017 13
6.0 OPTIONS
This section discusses the options available for the Liebert STS2. The communications options are also
discussed in 12.0 - Communication Interfaces.
6.1 Programmable Relay Board
The Programmable Relay Board (PRB) provides a means to trigger an external device when an event occurs in
the Liebert STS2. Each PRB has eight channels. Each channel has one set of Form-C dry contacts.
Any alarm/event can be programmed to any channel or channels. Up to ten (10) events can be programmed to a
relay. If multiple events are grouped to one relay, group the events logically to simplify troubleshooting when an
event is triggered. The same alarm/event can be programmed to more than one channel. Up to two
Programmable Relay Boards can be installed in the Liebert STS2 for a total of 16 channels. Programming is
performed through the touchscreen display.
See Configuring the Programmable Relay Board Settings on page 92 for default settings and instructions for
reconfiguring the relays. See Figures 19 and 20 for the location of the PRB. See Figure 22 for wiring details.
6.2 Optimized Transfer
When the Liebert STS2 is used as a primary-side switch—on the primary of an isolation transformer—optimized
transfer greatly reduces the transformer magnetization current during automatic transfers through a new,
patented transfer control algorithm. The Liebert algorithm optimizes the transfer timing so that the volt-seconds
applied to the downstream transformer primary is balanced, minimizing peak saturation current.
The volt-second balance is achieved by directly computing the volt-second applied to the transformer during
transfer events and determining the optimum time to turn on the alternate source SCRs in order to balance the
volt-second within specified tolerance.
Optimized transfer also seeks to minimize the voltage disturbances while still maintaining transformer flux
balance. This unique flux balance algorithm does not just wait for the balance point to occur, but will pulse fire
the SCRs as soon as possible to minimize the voltage disruption. This results in far superior voltage waveforms
applied to the load.
6.3 Distribution Cabinet With I-Line Panelboard—100-600A Units Only
A distribution cabinet with a Square D I-Line panelboard offers space to plug in up to 10 three-pole branch
circuit breakers (100A-250A). The panelboard is rated at 600A with an overall short-circuit rating of
100,000 AIC.
The full-height cabinet mounts on either the right or left side of the Liebert STS2 and is fully enclosed with a
keylock door and an accent cover that permits access to the panelboard without exposing other portions of the
Liebert STS2.
6.4 Input Contact Isolator Board
The Input Contact Isolator Board (ICI) provides an Liebert STS2 module interface for up to eight external user
alarm or message inputs to be routed through the Liebert STS2’s alarm network. The eight contacts are normally
open dry contacts. When a contact closes, an event is triggered.
The Input Contact Isolator options are configured through the Input Contact Isolator dialog box, which is
accessed from the Comm Option dialog box on the touchscreen display. You also can program the alarm
messages through this dialog box. See Configuring the Input Contact Isolator Settings on page 91 for
instructions on configuring the connections.
See Figures 19 and 20 for the location of the ICI. See Figure 23 for wiring details.
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