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Operating the UPS
5.7 Operating the UPS
5.7.1 AC Input Mode (Normal Operation)
The following illustration shows circuit power flow when the UPS is operating normally in the
AC Input Mode. The rectifier includes a boost chopper circuit that converts the AC input power
into DC power. The boost chopper circuit maintains a constant voltage with current limiting
abilities for charging the batteries. The rectifier supplies a DC voltage of the proper level to the
inverter section. The inverter section generates a high quality sine wave output voltage. The
batteries are maintained in a constantly charged state when the UPS is in the “Normal
Operation Mode.”
Power flow in AC Input Mode
5.7.2 Bypass Mode
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").
Power flow in Bypass mode
5.7.2.1 Bypass Mode for Optional Alternate Input Models
Input
Power
Isolation
Transformer
Model
MCCB
Converter Inverter
Chopper
Batteries
Bypass
MBS
Output
Power
Input
Power
Isolation
Transformer
Model
MCCB
MBS
Bypass
Converter Inverter
Output
Power
Chopper
Batteries