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TOSHIBA
26
Operating the UPS
Operation Modes (Cont'd)
Battery Backup Mode
The following illustration shows power flow during the battery backup mode. When
commercial ac power failures occur, the UPS's batteries instantly begin supplying dc
voltage to the UPS's main inverter circuit. This circuit changes (inverts) the dc power into
ac power. The ac power is available at the unit's output. This back-up process will continue
until the UPS's battery voltage drops below a specific minimum level. When this occurs,
the batteries will stop supplying power to the load. This minimum level is the rated minimum
voltage (Vmin). The rated battery voltage chart on page 22 shows (Vmin). The battery
backup time and discharge process is explained on page 22.
EPO (Emergency Power Off) Function
These units are equipped with terminals for receiving an emergency power-off (EPO) "closed
contact" switch command from a remote location (see 'terminal block details' on page 13 and
terminalblock location on page 45-46). This safety feature enables quick shut-down of the UPS's
ac output and battery circuits. Usually the emergency power off switch is installed in a central
location that is easily accessible to personnel concerned with the operation of the UPS unit and
the load equipment connected to it. The EPO function is initiated by pressing the switch to the
closed "shutdown" position. The effect of using the EPO switch is the same whether the UPS
unit is in the ac input mode (see page 24), battery backup mode (see page 25), or the circuit
bypass mode (see page 24). The following figure shows the UPS condition after application of
the EPO switch.
Inverter
*Switches are
solid state
devices
Input
power
Surge
absorber
MCCB
Line Filter
Input
fuse
Rectifier/
Chopper
Batteries
+
_
Bypass
*Static
switch
Isolation
Transformer
Output
fuse
Line Filter
Output
power
Power flow
Power flow in battery backup mode for all models
Inverter
*Switches are
solid state
devices
Input
power
Surge
absorber
MCCB
Line Filter
Input
fuse
Recti fier/
Chopper
Batteries
+
_
Bypass
*Static
switch
Isolation
Transformer
Output
fuse
Line Filter
Power flow
Output
power
(off)
TRIPPED
OFF
OFF