Powerware 9390 UPS 100160 kVA - Manual (Page 65)

UNDERSTANDING UPS OPERATION
EATON Powerware ® 9390 UPS (20–80 kVA) Installation and Operation Manual S 164201603 Rev 2 www.powerware.com 7-13
If at any time during the battery discharge the input power becomes available again,
the rectifier begins to supply DC current to the inverter. At this point, the unit returns
to Normal mode. If at any time during the battery discharge the AC input power
becomes available again, each rectifier turns on, assumes the inverter load from the
batteries, and begins recharging the batteries. Depending on the total load and the
duration of the battery discharge, battery and rectifier input current limit alarms may
be seen for a short time due to the current required to recharge the batteries.
7.3 Functional Description
The UPS is a true online double-conversion unit with a transformerless power train.
A high-frequency active rectifier powers a high-frequency three-phase inverter. The
bypass circuit uses a solid-state continuous-duty static switch. The UPS operates
from battery strings from 192 cells (384V) to 240 cells (380V/400V/415V/480V).
7.3.1 Input Rectifier
The rectifier is a three-phase, high-frequency PWM, IGBT-based power conversion
stage that provides input power factor correction and low input current harmonic
distortion. The rectifier maintains a DC level that is optimized for maximum inverter
efficiency. A precharge system charges the energy storage elements in the power
train prior to energizing the rectifier.
7.3.2 Inverter
The inverter is a three-phase, high-frequency PWM, IGBT-based power conversion
stage that continuously supplies the critical load with high-quality AC power. The
IGBTs are modulated to maintain the highest efficiency.
7.3.3 Battery Charger and ABM
The charger is a high-frequency, IGBT-based power conversion stage. The UPS uses
ABM technology, which isolates the battery from the electrical environment, except
for periodic charging or reserve mode operation, extending its life.
ABM extends battery life by keeping the batteries charged and performing periodic
battery testing.
An ABM charging cycle starts with the charger driving the battery voltage, at
maximum current limit, to a battery charge level of 2.34 volts/cell. The time it takes
for the voltage to reach to the battery charge level is saved as the battery charge
time. If the battery charge time exceeds 100 hours, an alarm sounds.
As soon as a battery charge level of 2.34 volts/cell is reached, the battery is charged
at a float level of 2.31 volts/cell for 48 hours (battery float time) plus 150% of battery
charge time. Twenty-four hours into the float period, a series of battery tests are
performed to check the battery health. The float level charge continues after a
successful test.
At initial startup, the battery run time on the front panel display indicates two minutes.
After the 24-hour float charging period and battery testing, the actual battery run time
is determined and the actual battery run time is displayed.
After the float period is completed, the charger is disconnected and the batteries are
allowed to rest for 672 hours (28 days) maximum rest time. If the battery voltage falls
below the opportunity charge level of 2.1 volts/cell during the first 240 hours of the
rest period, an alarm sounds.