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Battery Mode
Upon failure of the AC mains input power, the inverter of power modules, which obtain power from the
battery, supply the critical AC load. There is no interruption in power to the critical load upon failure. After
restoration of the AC mains input power, the “Normal mode” operation will continue automatically without the
necessity of user intervention.
Fig 3-3 Battery mode operation diagram
Bypass Mode
If the inverter overload capacity is exceeded under Normal mode, or if the inverter becomes unavailable for
any reason, the static transfer switch will perform a transfer of the load from the inverter to the bypass source,
with no interruption in power to the critical AC load. Should the inverter be asynchronous with the bypass, the
static switch will perform a transfer of the load from the inverter to the bypass with power interruption to the load.
This is to avoid large cross currents due to the paralleling of unsynchronized AC sources. This interruption is
programmable but typically set to be less than 3/4 of an electrical cycle, e.g., less than 15ms (50Hz) or less than
12.5ms (60Hz). The action of transfer/re-transfer can also be done by the command through monitor.
Fig. 2-4 Bypass mode operation diagram
