Emerson 480V, 60HZ Maintenance Mode, Parallel Redundancy Mode System Expansion, Operation

Operation

Maintenance Mode

For maintenance or repair, the Liebert NX may be operated in maintenance mode. To place the Lie- bert NX in maintenance mode, the load must be transferred to bypass and the inverter must be turned off. When those conditions are met, the CB3 may be turned on and the UPS may be shut down, permitting disconnecting the batteries for maintenance.

! CAUTION

The internal maintenance bypass must not be used when the UPS system is in a parallel system.

! WARNING

The UPS input and output must be protected with external overcurrent protection devices. In maintenance mode, the input and output busbars remain energized.

Parallel Redundancy Mode (System Expansion)

For higher capacity, higher reliability or both, the outputs of up to four UPS modules can be pro- grammed for directly paralleling while a built-in parallel controller in each UPS ensures automatic load-sharing.

Frequency Converter Mode

The Liebert NX can be programmed into frequency converter mode for either 50Hz or 60Hz stable output frequency. The input frequency may vary from 57Hz to 66Hz. In this mode, the static bypass operation is disabled and the battery becomes optional, depending on any requirement to operate in battery mode (stored energy mode).

If ECO mode is selected, the double-conversion UPS operation is inhibited at most times for the pur- pose of saving energy. In this mode of operation, not unlike UPS of line-interactive or stand-by tech- nology, the bypass is the preferred source, and only when the voltage and/or frequency of the bypass supply is beyond pre-defined and adjustable limits is the critical AC load transferred to the inverter. This transfer takes place with an interruption of less than 3/4 of an electrical cycle, e.g., less than 15ms (50Hz) or less than 12.5ms (60Hz).

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