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UPS 225 - 275 kVA/300kVAPF0.8
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User’s and Installation Guide
Revision E
6 Understanding UPS operation
6.1 Looking inside the UPS system
The Eaton 9395 UPS is a continuous-duty, solid-state, transformerless (at 400 Vac), three-phase, true
online system that provides conditioned and uninterruptible AC power to the UPS system’s output and
critical load. The basic system consists of a rectifier, battery converter, inverter, monitoring/operation
control panel, integrated communication server, and digital signal processor (DSP) logic.
Figure 6-1. Main elements of the UPS system
NOTE
On a UPS configured as an Input Output Module (IOM), the bypass input, static switch, and
backfeed protection contactor (K5) are not present.
If utility power is interrupted or falls outside the parameters specified in Chapter 10: “Product
specifications” the UPS uses a backup battery supply to maintain power to the critical load for a
specified period of time or until the utility power returns. For extended power outages, the UPS allows
you to either transfer to an alternative power system (such as a generator) or shut down your critical
load in an orderly manner. The emergency bypass consists of a continuous-duty static switch and
backfeed protection contactor K5. The backfeed protection contactor is located in series with the static
switch. For manual transfers to bypass, the static switch is also used. The static switch is armed and
ready during both types of transfers.
On a UPS configured as an Input Output Module (IOM), bypass circuitry is not installed. This
configuration is primarily used in multiple UPS parallel systems that do not need a bypass for each UPS
and use a separate System Bypass Module (SBM) to provide system bypass capabilities.
