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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.
Converter Inverter
Bypass
Charger/
Chopper
Isolating
XFMR
External
Batteries
Output
Power
MCCB
MBS
Input
Power
Overcurrent
Low Batteryt
Input Abnormal
Overcurrent
Overload
Overvoltage/
Undervoltage
7.2 System Protection Functions
The following chart shows the built-in UPS fault protection functions on all models.
Built-in UPS Fault Protection Functions
Protection Item
Inverter Over-voltage
(IVOV)
Inverter Under-voltage
(IVUV)
UPS Overload
LCD Message
INVERTER
OVERVOLTAGE
INVERTER
UNDERVOLTAGE
OUTPUT OVERLOAD
Cause Control Malfunction; Feedback Error Overload or short circuit at the load.
Operation Mode
after Fault
Bypass Operation; Chopper and Inverter Stopped
Inverter Overload: Transfer to bypass; Inverter
stopped.
Bypass Overload: Inverter, Chopper, and Bypass
stopped.
Audible Alarm Yes: See Audible Alarm Functions
Visible Alarm Red Fault Lamp “on”
Inverter OL: No Fault Lamp
Bypass OL: Fault Lamp “on”
Relay Contact
Alarm
Fault Relay closed; Bypass Relay closed
Inverter OL: Bypass Relay closed
Bypass OL: Bypass Relay open and Fault relay
closed
Auto-Retransfer No
Inverter OL: Yes, if bypass ok
Bypass OL: No
Protection Item
Low Battery Voltage
(Level-1)
Low Battery Voltage
(Level-2)
Inverter Output Current Limit
LCD Message
Line-4 will read
“BATTERY LOW”
DC UNDERVOLTAGE OUTPUT OVERLOAD
Cause Battery Discharge
Battery Shutdown Level
reached
Load Inrush current
Operation Mode
after Fault
Battery Discharge
Shutdown: If Bypass ok, transfer to bypass; if not, current-limit
mode
No Output
Audible Alarm Yes: See Audible Alarm Functions
Visible Alarm Battery Lamp Flickers NO NO
Relay Contact
Alarm
Low Battery Relay
closed
Bypass Relay closed
Auto-Retransfer No Yes, if bypass ok
4200FA CT/XT User’s Manual 60