User manual

30 Chapter 4 Operation
NXr UPS Module And Parallel System 30kVA ~ 200kVA User Manual
4.3.1 Normal Mode
The UPS rectifier derives power from the AC mains input source and supplies DC power to the inverter, which
continuously supplies the AC load to the load. Simultaneously, the charger, which derives power from the rectifier,
float or boost charges the associated backup battery of the UPS.
4.3.2 Battery Mode
The UPS is operating in battery mode when the battery is supplying backup power to the load through the inverter.
Upon mains failure, the UPS automatically transfers to battery mode without power interruption to the load. Upon
restoration of the AC mains, the UPS automatically transfers back to normal mode without the necessity of user
intervention, without power interruption to the load.
Note
Battery start function is available for switching the UPS on into battery (charged) mode directly upon mains failure. Thus, the
battery power can be used independently to increase the UPS utility.
4.3.3 Automatic Restart Mode
The battery becomes exhausted following an extended AC mains failure. The inverters shut down when the battery
reaches the EOD voltage. The UPS can be programmed to automatic restart after EOD after a set variable delay time.
This mode and any delay time are programmed by the commissioning engineer.
4.3.4 Bypass Mode
During normal mode operation, if the inverter fails, is overloaded or turned off, 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 load. Should the
inverter be asynchronous with the bypass, the static transfer switch will perform a transfer of the load from the
inverter to the bypass, with interruption in power to the load. This is to avoid paralleling of unsynchronised AC sources.
This interruption is programmable but typically set to be less than 3/4 of an electrical cycle, for example, less than
15ms (50Hz) or less than 12.5ms (60Hz).
4.3.5 Maintenance Mode (Manual Bypass)
If UPS maintenance or repair is needed, you may use the maintenance switch to transfer the load to the maintenance
bypass, with no interruption in power to the load. This maintenance switch is fitted in all UPS modules and rated for
full load of one module.
4.3.6 Parallel Redundancy Mode (System Expansion)
For higher capacity or higher reliability or both, the outputs of multiple UPS modules can be programmed for directly
paralleling while a built-in parallel controller in each UPS ensures automatic load sharing. The parallel system can be
composed of up to four UPS modules.
4.4 Battery Management (Set During Commissioning)
4.4.1 Normal Function
1. Constant current boost charge.
The charge current can be set.
2. Constant voltage boost charge.
The boost charge voltage can be set as required by the type of battery.
For valve-regulated lead-acid (VRLA batteries, the maximum boost charge voltage should not exceed 2.4V/cell.
3. Float charge.