Embraer EMB145 - Page 1709

ELECTRICAL
AIRPLANE
OPERATIONS
MANUAL
2-05-05
Page
8
Code
01
REVISION 36
AOM-145/1114
APU STARTER-GENERATOR
A 28 V DC, 400 Amperes, APU-driven starter-generator supplies
electrical power during ground operation or in flight, as an alternative
source of electrical power. The APU starter generator is controlled and
protected by its dedicated GCU.
The APU Generator Button, on the Electrical System Panel, must be
pressed for normal operation. The APU line contactor is actuated on
and off by APU speed. If a failure occurs on the APU generator, a
reset may be attempted releasing the APU Generator Button and
pressing it again. Only one reset may be attempted.
The APU generator, when operating, is connected in parallel with the
generators supplying DC Bus 2. If needed, the APU generator can
replace an inoperative left network generator. After starting, and with
an engine driven generator inoperative, the APU generator
automatically replaces the inoperative generator.
Three electrical sources may be used to power an APU start: ground
power unit, battery 2 or battery 2 assisted by the main generators.
Battery 1 cannot be used for APU starting. Instead, it is isolated from
the load buses to provide stable electrical power to supply equipment
that may be affected by voltage fluctuation.
During starting, the APU Starting Contactor (ASC) is closed, allowing
the APU starter-generator to operate as a starter, energized through
the Central DC Bus. When the APU starting cycle is completed, the
ASC opens. A caution message is displayed on the EICAS if the ASC
does not open.
At 95% RPM plus seven seconds, the APU starter generator is
available to supply electrical power to the system. In this condition, the
APU Line Contactor (ALC) is closed, connecting the APU starter
generator to the load buses. If the ALC does not close due to
contactor failure or button not pressed, a caution message is displayed
on the EICAS.
The APU starter generator voltage and current may be monitored on
the MFD.