Tripp Lite PDUMH20ATNET, PDUMH15ATNET Configuration and Operation, Automatic Transfer Switch

Configuration and Operation

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).

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	< Vin < 139V	Good
75V	< Vin < 99V	Fair
Vin < 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.

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.

Utility B	Utility A
Facility Circuit	Facility Circuit
Secondary UPS	Primary UPS
Secondary Input Cord	Primary Input Cord
Critical Equipment	PDUMH15ATNET
Loads

10