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Powerware 9335 (80 kVA and120 kVA) Installation and Operation 5-5
164201396 REV. A 071103
The DC boost converter derives power from the unregulated DC rectifier and produces a
higher, stable DC voltage and current source for the inverter. A fixed system neutral is also
carried through the boost converter to allow full support of single phase AC loads from any
phase of the inverter output. The output neutral of the system is connected to the required
neutral, both from the main utility supply and the bypass supply and should never be bonded
to protective earth ground at the UPS output.
The inverter produces three phase AC power to a customer load without the use of a
transformer. The inverter derives power from the boost converter regulated DC and utilizes
IGBT devices and pulse-width modulation (PWM) to produce a regulated and low harmonic
content AC output. The AC output of the inverter is delivered to the system output through
the output contactor K2.
If the utility AC power is interrupted or is out of specification, the UPS automatically switches
to Battery mode to support the critical load with no interruption. When utility power returns,
the UPS returns to normal mode.
If the UPS becomes overloaded or unavailable, the UPS switches to Bypass mode. The
UPS automatically returns to Normal mode when the overload condition is cleared and
system operation is restored within specified limits.
If the UPS experiences an internal failure, it switches automatically to Bypass mode and
remains in that mode until the failure is corrected and the UPS is back in service.