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Chapter 5
Understanding UPS Operation
5.1
UPS System Overview
The Eaton 93PM UPS is a continuous-duty, solid-state, transformerless, 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 5-1 shows the main elements
of the UPS system.
If utility power is interrupted or falls outside the parameters specified in Chapter 9, "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 static switch, and bypass switchgear. The bypass switchgear
is located in series with the static switch. The static switch is armed and ready during normal operation.
This unit is a four-wire device. The loss of a single input phase or the loss of neutral with unbalanced four-wire
loads will be considered a complete loss of input power and discharge the battery to provide power to the load.
AC Input to
Rectifier/
Charger
AC Input to
Bypass
Figure 5-1. Main Elements of the UPS System
Eaton 93PM UPS (20–50 kW, 480V Four Wire – 50 kW Frame) Installation and Operation Manual P-164000540—Rev 4
Battery
Switchgear
Rectifier
Switchgear
Rectifier
Static
Switch
Bypass
Switchgear
UPS Cabinet
Battery
Battery
Converter
Inverter
Power Module
Digital
Metering
www.eaton.com/powerquality
Inverter
Switchgear
AC Output
to Critical
Load
5-1
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