Single Ups; Modes; Online Mode - Eaton Power Xpert Plus 1 Installation And Operation Manual

UNDERSTANDING UPS OPERATION
6.2

Single UPS

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6-2
Power Xpert 9395 UPS (450–550 kVA) Installation and Operation Manual
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.
A single UPS operates independently to support an applied load from the inverter,
providing conditioned and uninterruptible AC power to the critical load from the output
of the module. During an outage, the inverter continues to operate, supporting power
to the load from the battery supply. If the unit requires service, applied loads are
transferred to the internal bypass, continuous-duty static switch either automatically
or manually. With the exception of a battery cabinet, no other cabinets or equipment
are required for the single UPS to successfully support its applied loads.
6.2.1

Modes

The Power Xpert 9395 UPS supports a critical load in three different modes of
operation:
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In Online mode, the critical load is supplied by the inverter, which derives its power
from rectified utility AC power. In this mode, the battery charger also provides
charging current for the battery, if needed.
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In Energy Saver mode, commercial AC power is supplied directly to the critical load
through the continuous static switch and transfers automatically to Online mode if
an abnormal condition is detected. The Energy Saver mode requires a UPS with a
continuous static switch.
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In Variable Module Management System mode, the UPS operates as a traditional
double-conversion UPS, but selectively shifts the load to fewer UPMs to increase
the efficiency of the UPS.
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In Bypass mode, the critical load is directly supported by utility power.
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In Battery mode, the battery provides DC power, which maintains inverter
operation. The battery supports the critical load.
The following paragraphs describe the differences in the four UPS operating modes,
using block diagrams to show the power flow during each mode of operation.
6.2.2

Online Mode

Figure 6‐2 shows the path of electrical power through the UPS system when the UPS
is operating in Online mode.
During normal UPS operation, power for the system is derived from a utility input
source through the rectifier input contactor K1. The front panel displays "Normal,"
indicating the incoming power is within voltage and frequency acceptance windows.
Three-phase AC input power is converted to DC using IGBT devices to produce a
regulated DC voltage to the inverter. When contactor K2 is closed the battery is
charged directly from the regulated rectifier output through a buck or boost DC
converter, depending on the system voltage and the size of the battery string
attached to the unit.
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