Operating The Ups; Ac Input Mode (Normal Operation); Circuit-Bypass Mode - Toshiba 4200FA User Manual

6.0 Operating the UPS

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.
Power Flow
Isolating
XFMR
Input
Power
Power flow in AC input mode for the 4200FA 75/80 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).
Power Flow
Isolating
XFMR
Input
Power
Power flow in circuit-bypass mode for the 4200FA 75/80 kVA UPS
T O S H I B A
MCCB
Converter
MCCB
Converter
36
Static
Bypass
Inverter
Charger/
Chopper
External
Batteries
Static
Bypass
Inverter
Charger/
Chopper
External
Batteries
Output
Power
Output
Power