171600XPi Series UPS Installation and Operation Manual – 60616-014
9 Operating Modes
9.1 Static-Bypass (Stop operation)
If the UPS unit is severely overloaded or develops an internal fault, power ow is automatically switched from the unit’s main
circuit to the bypass circuit. Power ow through the bypass is shown in the following illustration. This change-over occurs
automatically in phase in less than one-quarter cycle of the input waveform. The switching period is not long enough to
cause interruptions to occur in most loads.
• If the power ow is transferred to the bypass circuit due to an internal fault the UPS will continue to supply power to
the load through the bypass and indicate a system fault message (see “24.3 System Fault Messages” on page 52).
• If the power ow is transferred to the bypass circuit due to an overload condition (see “24.4 System Warning Messages”
on page 55), then the power ow will automatically transfer from the UPS’s bypass circuit back to the inverter circuit
after removing the overload if set to do so (AutoXfer parameter (Cmd ID 660)).
POWER FLOW IN BYPASS FOR ALL MODELS
Output
Power
Line Filter Inverter
*Static Switch
Isolation
Transformer
Input
Power
Input
Fuse
Power Flow
Bypass
* Switches are
solid state
devices.
MCCB
Output
Fuse
Surge
Absorber*
Batteries
+
–
Rectier/
Chopper
Negative Bus
9.2 On-Line (Run operation)
The following illustration shows circuit power ow when the UPS is operating normally in the On-Line mode. The UPS
rectier, including a boost chopper circuit, converts AC input power to DC power. The boost chopper circuit maintains a
constant voltage, with current limiting, for charging the batteries. The inverter section generates a high quality sinu soidal
output voltage. The unit’s batteries are always maintained in a constantly charged state when the UPS is in the run operation
mode.
Output
Power
Line Filter Inverter
*Static Switch
Isolation
Transformer
Input
Power
Input
Fuse
Power Flow
Bypass
* Switches are
solid state
devices.
MCCB
Output
Fuse
Surge
Absorber*
Batteries
+
–
Rectier/
Chopper
POWER FLOW IN ON-LINE MODE FOR ALL MODELS
Negative Bus
*Surge Absorber is connected as indicated in 3.6–10kVA units. Surge Absorber is connected at the point between the Line Filter and Input Fuse in 14–22kVA units.