Powerware 10001100 kVA operation manual Path of Current Through the UPS in Battery Mode

UNDERSTANDING UPS OPERATION

During a utility power failure, the rectifier no longer has an AC utility source from which to supply the DC output current required to support the inverter. The input contactor K1 opens and the battery instantaneously supplies energy to the battery converter. The converter either bucks or boosts the voltage so that the inverter can support the customer’s load without interruption. If bypass is common with the rectifier input, the backfeed protection contactor K5 also opens. The opening of contactors K1 and K5 prevent system voltages from bleeding backwards through the static switch and rectifier snubber components and re−entering the input source.

Bypass

Breaker

(CB4)

Bypass Input

Input

Breaker

Rectifier (CB1

Input

Rectifier

K1

Static

Switch

K5

Inverter

K3

Output

Breakers Contactors

Closed

Open

Battery

Converter

K2

Battery

Breaker

Battery

Main Power Flow

Trickle Current

Energized

De−Energized

Figure 6-4. Path of Current Through the UPS in Battery Mode

If the input power fails to return or is not within the acceptance windows required for normal operation, the battery continues discharging until a DC voltage level is reached where the inverter output can no longer support the connected loads. When this event occurs, the UPS issues another set of audible and visual alarms indicating SHUTDOWN IMMINENT. Unless the rectifier has a valid AC input soon, the output can be supported for only two minutes before the output of the system shuts down. If the bypass source is available, the UPS transfers to bypass instead of shutting down.

If at any time during the battery discharge the input power becomes available again, contactors K1 and K5 close and the rectifier begins to supply DC current to the converter and inverter. At this point, the unit returns to Normal mode. Depending on the total load and the duration of the battery discharge, battery current limit alarms may be seen for a short time due to the current required to recharge the battery.

EATON Powerware® 9395 UPS (1000–1100 kVA) Installation and Operation Manual S 164201764 Rev 1 www.powerware.com 6−5