4.2 Modes

The Powerware 9395 UPS supports a critical load in three different modes of operation.The UPS can automatically use all three modes, as required.The standard operation modes are:

In 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 Battery mode, the battery provides DC power, which maintains inverter operation.The battery supports the critical load.

In Bypass mode, the critical load is directly supported by utility power.The following paragraphs describe the differences in the three UPS operating modes, using block diagrams to show the power flow during each mode of operation.

4.2.1 Normal mode

Figure 4-2 shows the path of electrical power through the UPS system when the UPS is operating in normal mode.

Figure 4-2. Path of current through the UPS in normal 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. The battery is charged directly from the regulated rectifier output through a buck or boost DC converter, depending on whether the system voltage and the size of the battery string attached to the unit.

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.

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UPS 450 - 550 kVA (2x225 - 2x275 kVA)

1027574

 

User’s and Installation Guide

Revision B