Guide Specification – 3-Phase Static Uninterruptible Power Supply
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5.2.3 Battery Protection
The converter shall be provided with monitoring and control circuits to protect the battery
system from damage due to excessive discharge. Converter shutdown shall be initiated
when the battery voltage reaches a discharge cutoff voltage of 400 VDC. Automatic
shutdown based on discharge time is not acceptable.
5.2.4 DC Ripple
AC Ripple on the DC Bus shall be less than 0.2%.
AC Ripple on the Battery charging circuit shall be less than 0.23% for the 80/100/160
kVA UPS, and less than 0.29% for the 225 kVA UPS.
5.3
IGBT Inverter:
5.3.1 General
The inverter shall be composed of multi-level IGBT power transistors controlled utilizing
an Advanced Technology PWM logic. The Inverter shall continuously convert DC power
from the IGBT Rectifier to AC power for the critical loads. When the utility voltage or
frequency exceeds the specified UPS input tolerances, the inverter shall continuously
convert DC power from the battery source to AC power for the critical load.
The inverter shall be capable of providing rated output while operating at any battery
voltage within the battery operating range. When the DC battery voltage reaches the
operational low voltage limit during a loss of utility AC power, the inverter shall
automatically shut off.
5.3.2 Output Voltage
The Inverter output voltage shall not deviate by more than +/- 1.0% RMS under the
following steady state conditions as the Inverter DC input varies from maximum to
minimum:
0% to 100%Unbalanced load
0% to 100%Balanced load
5.3.3 Synchronization
The Inverter output voltage shall be automatically synchronized with the bypass AC
source as long as the source is within the tolerable frequency and voltage range. If the
bypass AC source is not within the range, the control circuitry will stop synchronization
and operate the inverter in free running mode. When the bypass AC source recovers to
within tolerance, the inverter shall change its frequency (slew rate 1Hz/sec) and track the
bypass AC source until synchronization is achieved without causing any disturbance to
the load.
5.3.4 Output Control
The Inverter can be manually started and stopped using the LCD touch screen controls.
