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Facility Circuit Facility Circuit
PDUMH15ATNET
Critical Equipment
Loads
Secondary UPS
Primary UPS
Primary Input Cord
Secondary Input Cord
Utility B
Utility A
13
5. Configuration and Operation
5.1 Automatic Transfer Switch
When the Primary and Secondary inputs are both connected to Tripp Lite UPS Systems, the
PDU operates as an Automatic Transfer Switch, providing redundant input power for high
availability applications. Under normal operating conditions, the PDU will distribute power from
the Primary input source, switching to the Secondary input source under certain conditions.
The PDU will switch to the Primary source whenever it is Good according to the PDU input
voltage definitions (see below).
5.1A
Preferred Configuration
The Automatic Transfer Switch function
provides increased availability when the
Primary and Secondary inputs of the PDU
are connected to separate Tripp Lite UPS
Systems that are connected to separate
utility power sources. For maximum
availability, Tripp Lite recommends using
matching SmartOnline UPS Systems with
pure sine wave output for the Primary and
Secondary input power sources. The
automatic transfer switch function will be
compromised if the primary and secondary
inputs are connected to the same utility
power source.
Warning: DO NOT connect the primary
input to a line-interactive UPS, due to
transfer time issues, or to any source
that does not supply a pure sine wave.
Such sources may be used to power the
secondary input.
5.1B
Automatic Transfer Switch Source Selection
Upon power-up, the PDU looks for a source ≥85V. If it is unable to find a source ≥85V, it
remains off.
Input voltage definitions:
99V ≤ V
in
< 139V Good
75V ≤ V
in
< 99V Fair
V
in
< 75V Bad
In normal operation (after power-up), if the selected source is no longer Good, the PDU will
attempt to switch to the other source, but only if the other source is Good. If the selected
source becomes Fair and the other source is not Good, the PDU will keep the loads
connected to the selected source until the selected source becomes Bad, at which point the
loads will be disconnected (note that the source selection doesn't change). After the loads are
disconnected, they remain disconnected until the selected source becomes ≥85V, or until the
other source becomes Good.
21-02-124 933E0A.indb 1321-02-124 933E0A.indb 13 3/25/2021 2:19:11 PM3/25/2021 2:19:11 PM
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