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7.0 UPS Protection System
7.1 System Protection Features
The preceding one-line schematic illustrates the electrical locations of the protection devices on all UPS models.
Input Abnormal
MBS
(Not available for LT units)
Overcurrent
Overload
Bypass
MCCB
Input
Power
Isolating
XFMR
Converter Inverter
Output
Power
Overcurrent
Low Battery
Charger/
Chopper
Overvoltage/
Undervoltage
External
Batteries
7.2
Protection Item
System Protection Functions
The following chart shows the built-in UPS fault protection functions on all models.
Built-in UPS Fault Protection Functions
Inverter Over-voltage
(IVOV)
Inverter Under-voltage
(IVUV)
UPS Overload
LCD Message
Cause
Operation Mode after Fault
Audible Alarm
Visible Alarm
Relay Contact
Alarm
Auto-Retransfer
INVERTER
OVERVOLTAGE
INVERTER
UNDERVOLTAGE
Control Malfunction; Feedback Error
OUTPUT OVERLOAD
Bypass Operation; Chopper and Inverter Stopped
Overload or short circuit at the load.
Inverter Overload: Transfer to bypass; Inverter stopped.
Bypass Overload: Inverter, Chopper, and Bypass stopped.
Red Fault Lamp “on”
Yes: See Audible Alarm Functions
Inverter OL: No Fault Lamp
Bypass OL: Fault Lamp “on”
Fault Relay closed; Bypass Relay closed
No
Inverter OL: Bypass Relay closed
Bypass OL: Bypass Relay open and Fault relay closed
Inverter OL: Yes, if bypass ok
Bypass OL: No
Protection Item
LCD Message
Cause
Operation Mode after Fault
Audible Alarm
Visible Alarm
Relay Contact
Alarm
Auto-Retransfer
Low Battery Voltage
(Level-1)
Line-4 will read
“BATTERY LOW”
Battery Discharge
Battery Discharge
Battery Lamp Flickers
Low Battery Relay closed
No
Low Battery Voltage
(Level-2)
DC UNDERVOLTAGE
Inverter Output Current Limit
OUTPUT OVERLOAD
Battery Shutdown Level reached
Shutdown:
No Output
Load Inrush current
If Bypass ok, transfer to bypass; if not, current-limit mode
Yes: See Audible Alarm Functions
NO NO
Bypass Relay closed
Yes, if bypass ok
4200FA Installation and Operation Manual 67
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