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990-2359A Smart-UPS® VT 10-30kVA, 200/208V and XR Battery Enclosure Operation Guide 5
Operation Modes
In a stand-alone installation, the UPS has four different operating modes. If the installation includes a
Maintenance Bypass Panel, bypass mode and test mode will also be available.
Normal operation
During normal operation, the UPS converts utility power to conditioned power for the connected load.
Battery operation
During battery operation, the UPS provides power to the connected load from its internal and (if
applicable) external batteries for a finite period. The UPS transfers to battery operation if the supply
of utility power fails, or is outside pre-defined limits.
Bypass operation (or static bypass operation) utility
Static bypass operation can either be obtained by user request or automatically, as the UPS will
switch into bypass operation if both the normal and battery operation modes are unavailable. During
static bypass operation, the utility power is sent through internal Radio Frequency Interference (RFI)
filters to the connected load, bypassing the internal power converters. The UPS transfers to bypass
operation following a command received via the user display, or after a short or heavy overload on
the output of the UPS. Battery back-up is not available in bypass operation.
Mechanical bypass
In mechanical bypass, utility power is sent directly to the connected load through a mechanical
breaker, bypassing all internal UPS functions and filters. Mechanical bypass is obtained by the
operation of the mechanical bypass breaker lever located behind the front cover. Mechanical bypass
is a feature designed to keep the load supplied with utility power at maintenance of the power
sections of the UPS. All major maintenance operations can be performed with the UPS running in
mechanical bypass, and with the load being supplied directly with unconditioned utility power.
Wrap-around maintenance bypass
The UPS can be connected to an external Maintenance Bypass Panel. When activated, this panel bypasses
the entire UPS Enclosure (only possible with an optional APC Maintenance Bypass Panel), feeding utility
power directly to the load. An activated wrap-around Maintenance Bypass Panel completely isolates the
UPS and allows maintenance to be performed - including a replacement of the entire UPS.