TOSHIBA
6.0 Operating the UPS
6.9 Operation Modes
6.9.1 AC Input Mode (normal operation)
The following illustration shows circuit power flow when the UPS is operating
normally in the ac input mode. The UPS unit's rectifier, included in a boost
chopper circuit, converts ac input power to dc power. The boost chopper circuit
maintains a constant voltage, with current limiting, for charging the batteries. It
also supplies a dc voltage of the proper level to the inverter section. The inverter
section generates a high quality sinewave output voltage. The unit's batteries are
always maintained in a constantly charged state when the UPS is in the normal
operation mode.
6 - 5
Power flow in AC input mode for the 2.4, 3.6, 6 and 8 kVA Models
Input
power
MCCB
Batteries
Inverter
Rectifier/
charger/
chopper
Line
filter
Surge
absorber
*Static
switch
Isolation
Transformer
Output
power
Bypass
Power flow
* Switches are
solid state devices
6.9.2 Circuit-bypass Mode
If the UPS unit is severely overloaded or develops an internal fault, power
flow is automatically switched from the unit's main circuit to the bypass circuit.
Power flow through the bypass is shown in the following illustration. This
change-over occurs automatically in less than 4 milliseconds in phase. The
switching period is not long enough to cause interruptions to occur in most loads.
If the power flow is transferred to the bypass circuit because of an overload and
that overload condition ends within a specified period of time then the power flow
will be "re-transferred" to the AC input mode (normal operation) automatically. If
the power flow is transferred to the bypass circuit due to a fault condition,
then the power flow must be transferred manually from the UPS's bypass
circuit back to the inverter circuit after repairing the fault. This may be
possible by toggling the STOP/RUN switch (on the unit's front panel) first to
STOP and then back to RUN. This action resets (clears) the non-fatal faults (See
Restart Procedures Section 6.5).
Power flow
Power flow in circuit-bypass mode for 2.4, 3.6, 6 and 8 kVA Models
Rectifier/
charger/
chopper
Line
filter
Surge
absorber
MCCB
Input
power
Inverter
*Static
switch
Isolation
Transformer
Output
power
Batteries
* Switches are
solid state devices
Bypass
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