Reference Manual

Unit Description, BFU-21 and BFU-22

BFU-22 has one high-power TM output for supply of transmission

equipment.

18.2 Functions

The BFU supplies battery backed-up system voltage to the RBS and

disconnects the battery when it has reached its lower discharge limit.

The Contactor can disconnect and connect the battery with a control

signal from the Supervision Module (SM).

The BFU can supply priority power to transmission equipment. Power

to transmission equipment can be distributed even if a battery is not

present. The relay can select the power source with a control signal

from the SM.

BFU-21 also supplies priority power to the EC output. The EC output

is protected from reverse currents by a diode. Power to the EC output

can be distributed even if a battery is not present. The relay can select

the power source with a control signal from the SM.

The BFU communicates on the EPC bus (opto cable) with the DXU. If

the EPC bus is not present, the BFU operates at its default values. The

battery voltage, current and temperature are monitored and alarms are

sent on the EPC bus.

The BFU disconnects the battery, if the current is too low or the

temperature is too high. When the temperature returns to normal, the

battery is reconnected.

If the battery temperature sensor is faulty, a "Battery temperature sensor

fault" message is sent to the DXU.

The battery back-up can also be manually disconnected or disconnected

by control signals on the EPC bus.

The SM provides self-detection of internal faults and stores them in

non-volatile memory.

18.3 External Interfaces

P008641A

-2

Figure 115 BFU-21

EN/LZT 720 0008 P2A

2001-11-28

207 (485)

Preliminary