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Theory of Operation
11
Figure 6 UPS module block diagram
2.1.2 UPS Module
The UPS module consists of module controls, a rectifier/charger, an inverter, protective devices and
other accessories.
Module Controls: The module control logic monitors performance of the UPS module. The UPS
module status is displayed locally and is also sent to the System Control Cabinet.
Rectifier/Charger: The rectifier/charger converts utility power from AC to DC to charge the battery
and provide the DC input to the inverter. Its design limits reflected harmonic current distortion to
source power and provides low-ripple DC power for charging batteries. Multiple rectifier/chargers can
share a common battery plant, if that configuration is preferred for your application.
Inverter: The inverter converts DC power into the precise AC power required to supply a sensitive
critical load. The inverter converts DC power into a pulse-width-modulated (PWM)/six-step waveform
that is easily filtered into a clean sine wave output. The PWM/stepwave also minimizes the harmonic
voltage distortion caused by typical switching power supplies and other non-linear load components
used in computers and related electronics.
2.1.3 Battery Plant
The battery is used as the alternate source of power to supply DC power to the inverter if the AC sup-
ply voltage is outside the acceptable range. The battery supplies power to the inverter until the utility
power is restored or until an alternate power source is available. If AC source power is not restored or
an alternate power source is not available, the battery can be sized to provide power long enough for
an orderly shutdown of the load.
CB - Circuit Breaker
MBD - Module Battery Disconnect
SCC - System Control Cabinet
Rectifier/
Charger
Controls
CONTROL POWER
MULTI-MODULE UPS SYSTEM
Inverter
MBD
Utility
Input
Power
Control
Wiring
To SCC
Battery
Output
Power
To SCC
Output
CB
Input
CB