operates uninterruptedly during the conversion process and the UPS continues to supply uninterruptible
power to the load.
If both the UPS static bypass and the UPS rectifier are energized by AC power, the battery discharges to a
very low voltage when AC power and the static bypass cannot restore or AC power is not within the
specified limits required for normal system operation. As a result, the inverter cannot continue to supply
power to the load. When this event occurs, the UPS issues an audible and visual alarm indicating that the
battery has a minimal capacity left and the system shuts down in a short time. If AC power does not
become available again, the UPS can support output for a maximum of two minutes before the system
shuts down. If a bypass battery is available, the UPS transfers to Bypass mode instead of shutting down.
If AC power becomes available again during the battery discharge, K1 closes and the UPS returns to
Online mode. The UPS also starts to recharge the battery to restore the capacity.
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If any overload, load fault, or internal failure is detected, the UPS transfers automatically to Bypass mode.
The bypass source supplies AC power directly to the load . The UPS can also be commanded to transfer
to Bypass mode manually though the display. The front panel shows UPS status Bypass Mode. Figure
10: Path of current through the UPS in Bypass mode shows the path of electrical power through the UPS
system when the UPS is operating in Bypass mode.
CAUTION
The critical load is not protected in Bypass mode.
Figure 10. Path of current through the UPS in Bypass mode
1. Bypass input A Internal relay contact closed
2. Static switch B Internal relay contact open
3. Output C Main power flow
4. Inverter D Energized
5. Rectifier E De-energized
EATON 93T USER’S AND INSTALLATION GUIDE 614-40270
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December 2023 www.eaton.eu 2255
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