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4 Understanding UPS operation
4.1 Looking inside the UPS system
The Powerware 9395 UPS is a continuous-duty, solid-state, transformerless (at 400 Vac), three-
phase, true online system that provides conditioned and uninterruptible AC power to the UPS
system's output and critical load. The basic system consists of a rectifier, battery converter,
inverter, monitoring/operation control panel, integrated communication server, and digital.
Figure 4-1. Main elements of the UPS system
If utility power is interrupted or falls outside the parameters specified in Chapter 10, "Product
specifications, " the UPS uses a backup battery supply to maintain power to the critical load for a
specified period of time or until the utility power returns. For extended power outages, the UPS
allows you to either transfer to an alternative power system (such as a generator) or shut down
your critical load in an orderly manner. 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.
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Revision B
UPS 450 - 550 kVA (2x225 - 2x275 kVA)
User's and Installation Guide
41
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