Eaton Powerware 9390 Specifications download pdf (Page 58)

Understanding IAC Operation

4-2

EATON Powerware

9390 IAC-B and IAC-T Installation and Operation Manual S 164201590 Rev C powerware.com

4.1.2 Maintenance Bypass Mode

An MBP is u sed to safely supply utility power to the critical load during periods of UPS

maintenance or repairs. The bypass source supplies the commercial AC power to the load

directly.

When the MBP is closed, the load is wrapped around the UPS while power is still supplied

to the load by the UPS through the MIS. The MIS is then opened, isolating the UPS from

the bypass power source. The UPS c an be safely shut down and power removed from the

UPS without interrupting power to the critical load. If the optional BIB and RIB are

installed, the BIB and RIB are opened to remove power from the UPS. Otherwise, external

upstream breakers are used to remove power. The UPS now can be serviced or replaced

safely.

The critical load is not protected while the UPS is in Maintenance Bypass mode.

Figure 4-2 shows the path of electrical power through the IAC when operating in

Maintenance Bypass mode.

OUTPUT TO

CRITICAL LOAD

IAC

RIB

(OPTIONAL)

BIB

(OPTIONAL)

MIS

MBP

TO UPS RECTIFIER

INPUT

FROM UPS OUTPUT

TO UPS BYPASS

INPUT

MAIN POWER FLOW IN UPS MODE

MAIN POWER FLOW IN MAINTENANCE BYPASS MODE

AC INPUT TO

UPS FROM

UTILITY

AC INPUT TO

BYPASS FROM

UTILITY

Figure 4-2. Path of Current Through the IAC in Maintenance Bypass Mode

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Eaton Powerware 9390 Specifications Page 58