Emerson 30-200kVA User Manual

A group of paralleled modules behave as if it were one large UPS with the advantage of presenting 

higher reliability. In order to assure that all modules are equally utilised and to comply with relevant 

wiring rules, the following requirements apply:
1. All UPS modules must be of the same rating and must be connected to the same bypass source.
2. The bypass and the main input sources must be referenced to the same neutral potential.
3. Any RCD, Residual Current monitoring device, if installed, must be of an appropriate setting and 

located upstream of the common neutral bonding point. Alternatively, the device must monitor 

the combined 4-wire rectifier and split-bypass input currents of the system. Refer to the High 

Leakage Current Warning on page 1.

4. The outputs of all UPS modules must be connected to a common output bus.

5. Passive bypass current equalising chokes are available as an option in systems comprising more 

than three parallel redundant UPS modules (or two or more parallel capacity UPS modules).

The NX UPS is an on-line, double-conversion, reverse-transfer UPS that permits operation in these 

modes:

• Normal  Mode
• Battery Mode (Stored Energy Mode)
• Auto-Restart Mode
• Bypass Mode
• Maintenance Mode (Manual Bypass)
• ECO Mode
• Parallel Redundancy Mode
• Hot-Standby Mode
• Frequency Converter Mode

The UPS inverter continuously supplies the critical AC load. The rectifier/charger derives power from 

the AC mains input source and supplies DC power to the inverter while simultaneously FLOAT or 

BOOST charging its associated backup battery.

Upon failure of the AC mains input power; the inverter, which obtains power from the battery, sup-

plies the critical AC load. There is no interruption in power to the critical load upon failure or restora-

tion of the AC mains input power after which the “Normal Mode” operation will continue without the 

necessity of user intervention. 

The battery may become exhausted following an extended AC mains failure. The inverter shuts down 

when the battery reaches the End Of Discharge voltage (EOD). The UPS may be programmed to 

“Auto Recovery after EOD” after a delay time. This mode and any delay time are programmed by the 

commissioning engineer.

NOTE
Optional isolation transformers are available for applications where sources do not share the