Eaton 9E10Ki Operations Instructions download pdf (Page 68)

Understanding UPS Operation

5-2 Eaton 9E UPS (20–30 kVA, 208/220V) Installation and Operation Manual 164202124—Rev 5 www.eaton.com/powerquality

5.2 Single UPS

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 either automatically or manually. With the exception of an optional

external battery cabinet, no other cabinets or equipment are required for the single UPS to successfully support

its applied loads.

5.2.1 Modes

The Eaton 9EUPS supports a critical load in four different modes of operation:

In High-Efficiency (HE) Normal mode, commercial AC power is supplied directly to the critical load through

the internal bypass and transfers automatically to Standard Normal mode (double-conversion on demand) if

an abnormal condition is detected. HE mode is the default normal operating mode.

In Standard Normal 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.

In Bypass mode, the critical load is directly supported by utility power.

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 UPS operating modes, using block diagrams to show

the power flow during each mode of operation.

5.2.2 High-Efficiency Normal Mode

When the UPS is operating in HE mode, commercial AC power is supplied directly to the critical load through

the internal bypass with the power module in a standby state. If a commercial power brownout, blackout,

overvoltage, undervoltage, or out-of-tolerance frequency condition occurs the system forward transfers to

normal mode (double-conversion on demand) or battery mode. When the input line returns to normal operating

range, the UPS returns to HE operation. For charging batteries in HE mode, the UPS will revert to normal mode

to charge the batteries, then return to HE mode when charge cycle is complete.

HE mode is the default normal operating mode, and not an alarm condition. While the UPS is in this mode, the

NORMAL light on the front display will illuminate.

5.2.3 Standard Normal Mode

During Standard Normal mode, power for the system is derived from a utility input source through the rectifier

input relay. Three-phase AC input power is converted to DC using IGBT devices to produce a regulated DC

voltage to the inverter. When the battery relay 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.

Figure 5-2 shows the path of electrical power through the UPS system when the UPS is operating in Normal

mode.

The battery converter derives its input from the regulated DC output of the rectifier and provides either a

boosted or bucked regulated DC voltage charge current to the battery. The battery is always connected to the

UPS and ready to support the inverter should the utility input become unavailable.

The inverter produces a three-phase AC output to a customer's load without the use of a transformer. The

inverter derives regulated DC from the rectifier and uses IGBT devices and pulse-width modulation (PWM) to

produce a regulated and filtered AC output. The AC output of the inverter is delivered to the system output

through the output relay.

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Eaton 9E10Ki Operations Instructions Page 68

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