BOMBARDIER Challenger 601-3A CL-600-2B16 Pilot Training Manual page 74

start the APU and to supply backup DC power
when a primary DC power source has failed
or is not available. It also supplements the
available DC power supply when the ADG is
the only source of airplane power.
DC STATIC CONVERSION
In normal operation, primary DC power is ob-
tained from the AC system through the use of
four separate and independent transformer-
rectifier units (TRU). Each TRU converts 3-
phase, 115-/200-VAC power into unregulated
28-volt DC. TRU 1, rated at 100 amps, is pow-
ered by AC bus 1 and feeds DC bus 1 (Figure
2-17). TRU 2, rated at 100 amps, is powered
by AC bus 2 and feeds DC bus 2. Essential TRU
1 is powered from the AC essential bus and es-
sential TRU 2 is powered by AC bus 2. Both
essential TRUs are limited at 30 amps and
feed the DC essential and the battery bus. Loss
of DC power on any bus is detected by bus
sensing relays which cause illumination of
the appropriate BUS OFF light on the electrical
control panel (Figure 2-15). If essential TRU
1 or 2 fails, the respective ESS TRUS 1 OFF
or 2 OFF light illuminates ( Figure 2-15).
LEGEND
UNPOWERED BUS
POWERED BUS
IDG 1 POWER
IDG 2 POWER
TRU 1 POWER
TRU 2 POWER
ESSENTIAL TRU 1 POWER
ESSENTIAL TRU 2 POWER
Figure 2-17. Primary DC Power Feed (Normal Operation)
2-14 CL 601-3A/R
MAIN AC BUS 1 ESS AC BUS
A17
TRU
1
DC UTILITY BUS 1
A69
DC TIE
CONT
A68
DC BUS 1
FOR TRAINING PURPOSES ONLY
FlightSafety Canada
CL-600-2B16 PILOT TRAINING MANUAL
TRUs 1 and 2 normally supply their own as-
sociated buses. If a TRU failure occurs, the
power distribution to DC buses 1 and 2, except
the utility buses (Figure 2-17), can be main-
tained by energizing DC bus ties which cross-
connect the outputs of TRU 1 and TRU 2.
These bus ties are controlled by switchlights
on the electrical control panel labeled "BUS
TIE CLOSED." Both BUS TIE CLOSED
switchlights would have to be illuminated to
replace either TRU 1 or TRU 2 (Figure 2-15).
When a DC tie relay is closed, the respective
utility bus is load shed.
Essential TRUs 1 and 2 are dedicated to the DC
essential bus and cannot be used to supply ei-
ther the No. 1 DC bus or No. 2 DC bus. If es-
sential TRU 1 or 2 falls, the DC essential bus
can be supplied from the operating essential
TRU (Figure 2-17), or in an emergency con-
dition (all AC power lost), by deploying the
ADG. During ADG operation, the battery bus
and the DC essential bus are connected.
During transfer to ADG, when the aircraft is in
a weight-off-wheels condition and the battery bus
is unpowered, the DC essential bus is supplied
from the battery direct bus via the DC emer-
gency tie control 2 contactor (Figure 2-24).
C2
ESS ESS
TRU 1 TRU 2
D9 D8
ESS DC BUS
D10
D5
EMER
DC 1 TC
BATT BUS
MAIN AC BUS 2
B29
B17
TRU
2
DC UTILITY BUS 2
DC TIE
CONT
D7
B69 B68
D4
DC BUS 2
L t é e
L t d .