6 Chapter 1 Overview
APM 300 Integrated UPS Single Module And Parallel System User Manual
1.4.2
Parallel System Requirements
A UPS system consisting of two paralleled UPS modules behave as if it were one large UPS with the advantage
of presenting higher reliability. To ensure that all modules are equally used 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 source.
2. Any RCD, if installed, must be of an appropriate setting and located upstream of the common neutral
bonding point. Alternatively, the device must monitor the protective earth current of the system. Refer to
Warning: high leakage current
before
Contents
.
3. The outputs of the two UPS modules must be connected to a common output bus.
1.5
Operation Mode
The UPS is an on-line, double-conversion, reverse-transfer UPS that permits operation in these modes:
Normal mode
Battery mode
Automatic restart mode
Bypass mode
Maintenance mode (manual bypass)
ECO mode
Parallel and redundancy mode
Dormancy mode
Common battery mode
Frequency converter mode
Dual bus (LBS) system mode
Normal mode
As shown in Figure 1-5, the UPS rectifiers derive power from the AC mains input source and supply DC power
to the inverters, which continuously supply the AC load. Simultaneously, the charger, which derives power
from the rectifiers, float or boost charges the associated backup battery of the UPS.
Rectifier input switch
Mains input
Battery charger
Output switch
Inverter
Rectifier
UPS output
Battery
Automatic inverter switch
Mains input
Rectifier input switch
Rectifier
Battery
Battery charger
Inverter
Automatic inverter switch
Output switch
UPS output
Figure 1-5
Schematic diagram of normal mode
Battery mode
As shown in Figure 1-6, the UPS is operating in battery mode when the battery is supplying backup power to
the load through the inverters. 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.
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