Filter
Top Products
Operation Description
11
2.0 OPERATION DESCRIPTION
There are two types of operations which can be performed with the Liebert Continuous Power-Tie
System.
• Create a continuous tie between the critical buses of two UPS systems
• Transfer of a critical load between two UPS systems
2.1 Continuous Power-Tie
The following sequence of operations describe the actions to take to continuously tie two UPS systems
together. See Figure 5.
Selecting a Line Sync Source
From the Continuous Power-Tie Control Panel, select SYS1 or SYS2 using the PRIMARY BYPASS
SELECT switch.
Should a fault occur with the UPS systems in parallel, the chosen line sync source becomes the bypass
source for the critical loads.
Synchronizing the UPS Systems
From the Continuous Power-Tie Control panel, press the SYNCHRONIZE SYSTEMS button. The
Power-Tie logic checks for proper state indications from the UPS systems and the circuit breakers.
The SYNCHRONIZE SYSTEMS button light turns on to indicate the UPS systems have begun syn-
chronizing to the selected primary bypass.
The PRIMARY BYPASS light from the selected UPS system (UPS System 1 or UPS System 2) turns
on to identify the primary bypass.
With the line sync controls tied, the continuous Power-Tie logic checks the inter-module sync signals
for coincidence. The Power-Tie logic ties the inter-module sync signals when coincidence occurs.
This redundant digital sync bus holds all modules in sync, with or without a bypass reference. Using
the redundant digital sync makes certain the individual modules of both systems are tightly con-
trolled to enable the parallel operation of the UPS systems.
The SYNCHRONIZING light on the Control Status panel turns on (and stays on) during synchroniza-
tion.
Checking for Phase, Voltage, and Capacity
The Power-Tie logic checks these UPS system parameters, phase, voltage, and capacity, to determine
if they are within their proper limits. The OK TO TIE SYSTEMS light (from the CONTINUOUS TIE
CONTROL section of the control panel) turns on when these parameters are within their proper lim-
its.
OK to Tie UPS Systems
After the OK TO TIE SYSTEMS light turns on, press the PUSH TO TIE SYSTEMS AFTER OK but-
ton, on the CONTINUOUS TIE CONTROL panel. The TIE CB (tie circuit breaker) light turns on,
indicating the breaker has closed.
Both of the SYSTEMS TIED lights (on the LOAD 1 and LOAD 2 panels) turn on to indicate the tied
UPS system status.
With the two UPS systems in parallel, the voltage synchronization and power sharing loops become
tied. Together, these controls hold the module load sharing to within ±5% of load current. Should one
or the other control be inoperative, the Power-Tie logic can still maintain load sharing within accept-
able limits.
NOTE
Systems may be paralleled with the UPS systems initially separate or if both loads are initially
on one UPS system while the other was being serviced.