OPERATING INSTRUCTIONS
Eaton 9390 UPS, 9395 UPS, and 9395 SSBM Sync Control Installation and Operation Manual
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P-164000052 Rev 2
www.eaton.com/powerquality
4-2
To maintain a fault-tolerant arrangement, the Eaton Sync Control accounts for the
following fault conditions or abnormal operating conditions:
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An automatic reassignment of the preferred source (master) is made if the
non-master system goes to bypass, regardless of the position of the PREFERRED
SOURCE SELECTOR switch. When the non-master system (as defined by the
PREFERRED SOURCE SELECTOR switch) is on bypass, the non-master system
automatically becomes the master. The two systems continue to synchronize to
their own bypass source until one of the bypass sources becomes unavailable or
the two bypass sources are no longer in synchronization with each other.
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If one UPS/SSBM system loses its critical load bus voltage sensing, each system
synchronizes to its own bypass source regardless of the position of the
PREFERRED SOURCE SELECTOR switch.
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Dual redundant logic power supplies are incorporated within the Eaton Sync
Control, ensuring both systems remain synchronized even during the loss of one
of the logic power supplies. These power supplies are powered from each
system's critical load bus.
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With a complete loss of logic power to the Eaton Sync Control (due to component
failure or power supply fault), each system synchronizes to its own bypass source.
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(With optional Undervoltage relay) An automatic reassignment of the preferred
source (master) is also made if the preferred source loses its bypass reference.
When the master system (as defined by the PREFFERED SOURCE SELECTOR
switch) loses its bypass reference, the non-master system automatically becomes
the master allowing the other system to sync to a system with a good bypass.
Eaton Sync Control
Input
Source
System-A
To Critical Load-A Static
Transfer Switch
Input
Source
System-B
Bypass
Source
To Critical Load-B Static
Transfer Switch
Bypass
Source
Figure 4‐1. Typical Eaton Sync Control
Block Diagram with a Eaton 9390 UPS, Eaton 9395 UPS, or 9395 SSBM.
