TOSHIBA
6.1 Operating the UPS
6.1.1 AC Input Mode (normal operation)
The following illustration shows circuit power flow when the UPS is operating normally in the
AC input mode. The converter of the UPS, including a boost chopper circuit, converts the AC
input power to DC power. The boost chopper circuit maintains a constant voltage and provides
current limiting for battery charging. It also supplies a DC voltage of the proper level to the
inverter section. The inverter section generates a high quality sine wave output voltage. The
UPS batteries always maintain a charge during normal UPS operation.
Converter Inverter
Static
Bypass
Charger/
Chopper
Isolating
XFMR
Input
Power
MCCB
Power Flow
Output
Power
External
Batteries
Power flow in AC input mode for the 4200FA 80 kVA UPS
6.1.2 Bypass Mode
If the UPS detects an overload or develops an internal fault, power flow is automatically
switched from the main circuit of the UPS to the Bypass circuit. Power flow through the
Bypass is shown in the following illustration. This changeover occurs automatically in less than
4 milliseconds. 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 the
overload condition ends within a specified period of time, normal operation will resume
automatically (see Section 6.16 Overload Operation).
If the power flow is transferred to the bypass circuit due to a fault condition, the power flow
must be transferred manually from the Bypass circuit back to the inverter circuit after the fault
is cleared (see Section 6.11 Start-up Procedure).
Converter Inverter
Static
Bypass
Charger/
Chopper
Isolating
XFMR
External
Input
Power
MCCB
Power Flow
Batteries
Output
Power
Power flow in circuit-bypass mode for the 4200FA 80 kVA UPS
4200 FA User’s Manual 29