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OPM_SGS_USM_M75_M75_2US_V010.doc User Manual SG Series 750 UL S2 & SG Series 750 T12 UL S2
7.1.3 From External Maintenance Bypass (option) to normal function VFI
NOTE !
UPS system has been turned OFF following the “Maintenance shutdown (Load on
External Maintenance Bypass)” procedure and the Load is still powered by External
Maintenance Bypass (option) .
The Load must be transferred back to the UPS system .
Open the front door and make sure that:
•
The safety screens are fixed in their position.
•
The UPS Output Switch Q1 , Input Circuit Breaker CB4 , Battery Circuit Breaker are open (Pos. O)
and the External Maintenance Bypass Switch is closed (Pos. I).
•
LED Alarm is lit.
1. If not already supplied (separate utility inputs), switch-ON the utility power to the Rectifier
input.
2. Close the UPS Output Switch Q1 (Pos. I).
LED 1 (Utility Rectifier OK) must be lit.
The Load is supplied by the Utility through the UPS Automatic
Bypass and External Maintenance Bypass (option) .
The Synoptic Diagram must display the status “ LOAD
SUPPLIED BY AUTOMATIC BYPASS ” .
Input Circuit Breaker CB4 closes automatically. LED 3 (Rectifier ON) must blink.
The Rectifier starts up automatically, supplying the DC circuit , and charging the DC capacitors .
The LED 3 (Rectifier ON) stops blinking and stays ON, indicating that the DC link has reached the floating
voltage.
3. Connect the Battery to the UPS by closing (Pos. I) the Battery Circuit Breaker.
LED 4b (Charging Battery) should be lit indicating Battery Charge .
ATTENTION !
Before performing this operation, the LED 3 (Rectifier ON) must remain lit, thus
indicating that the DC-Link has reached floating voltage (540Vdc)!
4. Transfer the Load from External Maintenance Bypass (option) to UPS Automatic Bypass.
Use the External Maintenance Bypass panel instructions to transfer the Load from the External Maintenance
Bypass Breaker (MBB) to the UPS Automatic Bypass .
After this step, the Load is supplied by the Utility through the Automatic Bypass .
MBB Open, MIB(s) Closed, and “ LOAD SUPPLIED BY AUTOMATIC BYPASS ” must display on the Synoptic
Diagram .
5. Insert the Inverter by pressing the “Inverter ON” ( I ) key .
Soft-start of Inverter indicated with blinking LED 5 (Inverter available) .
At the end of Soft-start the LED 5 (Inverter available) remains lit.
Automatic transfer from Automatic Bypass to Inverter .
UPS output LED indicates Load on Inverter .
LED Alarm turn Off and the LED Operation must be lit.
The Synoptic Diagram must display the status “ LOAD
SUPPLIED BY INVERTER ” .
END OF PROCEDURE