Eaton 93PM-L 20 – 60 kW (208V) UPS Installation and Operation Manual P-164000711—Rev 03
105
Figure 52. Path of Current Through the UPS in Bypass Mode
Bypass Input
Rectifier Input
Rectifier
Switchgear
Main Power Flow
Trickle Current
Energized
De-Energized
Rectifier
Battery
Converter
Battery
Switchgear
Battery
Inverter
Inverter
Switchgear
Output
Static
Switch
Closed
Open
Switchgear
55..22..55
B
Baatttteerryy M
Mooddee
The UPS automatically transfers to Battery mode if a utility power outage occurs, or if the utility power does not
conform to specified parameters. In Battery mode, the battery provides emergency DC power that the inverter
converts to AC power.
shows the path of electrical power through the UPS system when operating in Battery mode.
During a utility power failure, the rectifier no longer has an AC utility source from which to supply the DC output
voltage required to support the inverter. The rectifier switchgear opens and the battery instantaneously
supplies energy to the battery converter. The converter boosts the voltage so that the inverter can support the
customer's load without interruption. The opening of the rectifier switchgear prevents system voltages from
bleeding backwards through the static switch and rectifier snubber components to the utility source.
If the input power fails to return or is not within the acceptance windows required for normal operation, the
battery continues discharging until a DC voltage level is reached where the inverter output can no longer
support the connected loads. When this event occurs, the UPS issues another set of audible and visual alarms
indicating SHUTDOWN IMMINENT. Unless the rectifier has a valid AC input soon, the output can be supported
for only two minutes before the output of the system shuts down. If the bypass source is available, the UPS
transfers to bypass instead of shutting down.
If at any time during the battery discharge the input power becomes available again, the rectifier switchgear
closes and the rectifier begins to supply DC current to the converter and inverter. At this point, the unit returns
to Normal mode. Depending on the total load and the duration of the battery discharge, battery current limit
alarms may be seen for a short time due to the current required to recharge the battery.
Summary of Contents for 93PM-L Series
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