American Power Conversion Smart-UPS - Manual (Page 19)

990-2818A Smart-UPS® VT ISX 20-30 kVA, 200 V Operation 13
Operation
Operation Modes
The UPS has four different operation 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)
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 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 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.