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58 4200FA Installation and Operation Manual
Bypass Mode 8.2
If the UPS unit is severely overloaded or develops an internal fault, power flow is automatically switched from the
main circuit to the Bypass circuit. Power flow through the bypass is shown in the following illustration.
This changeover occurs automatically in less than 4 milliseconds in phase (Make-Before-Break).
If the power flow is transferred to the Bypass circuit because of an overload, and that overload condition ends within a
specified period of time, then the power flow will "re-transfer" to the AC Input Mode (Normal Operation) automatically.
If the power flow is transferred to the Bypass circuit due to a fault condition, then the power flow must be
transferred manually from the UPS's Bypass circuit back to the Inverter circuit after repairing the fault (see
"Start-up Procedure").
If the power flow is transferred to the Bypass circuit due to an overload condition, then the power flow will
automatically transfer from the UPS's Bypass circuit back to the Inverter circuit after removing the overload
(see "Overload Operation").
Figure 8-2 Power Flow in Bypass Mode
Input
Power
Converter Inverter
Bypass
Charger/
Chopper
Isolating
XFMR
External
Batteries
Output
Power
MCCB
MBS
(Not available for LT units)
Power Flow