Learjet 60 - AC Circuit Breakers; AC Power Distribution; INVERTER Switches

Learjet
60

Pilot's Manual
AC POWER DISTRIBUTION
Electrical power for aircraft and
avionics systems requiring AC power
is supplied through two 115-volt, 400-Hz, 1500VA, solid-state
invert-
ers . During normal operation, the left and right inverter
output volt-
ages are applied to the left and right AC buses respectively
. The left
and right AC buses may be interconnected through the
7
.5-amp AC
BUS TIE circuit breaker/switch on the copilot's circuit breaker panel .
Each AC bus is intended to be
powered by only one inverter . There-
fore, the AC BUS TIE switch should
only be closed after removing
power from one of the buses and
setting the respective INVERTER
switch to OFF . If both INVERTER switches
are On, a relay in the copi-
lot's circuit breaker panel will prevent the AC BUS
TIE from function-
ing (electrically) . An inverter relay box controls 28
VDC input to the
inverters and provides isolation between the inverter
output and AC
bus should
an inverter fault occur . A phase lock function
within the
right
inverter keeps the output of each inverter
in-phase . Input power
to
operate the left and right inverters is 28
VDC supplied through
100-amp
current limiters connected to
the left and right generator
buses respectively .
INVERTER SWITCHES
Operation of the left and
right inverters is controlled through
the two
INVERTER switches on the
pilot's switch panel . The
switch control-
ling the left inverter is
labeled L-OFF and the switch
controlling the
right inverter is labeled
R-OFF . When either switch
is moved to the
On (L or R) position,
the associated power relay
is energized to sup-
ply input
power to the associated inverter
. When one switch is On
and the
other is OFF, a relay in the inverter relay
box is energized iso-
lating the inoperative
inverter from its associated
AC bus . The
invert-
er control circuits
operate on 28 VDC supplied
through the
2-amp L
INV and R INV
circuit breakers on the
pilot's and copilot's
circuit
breaker
panels respectively .
AC
CIRCUIT BREAKERS
The
aircraft AC electrical circuits
are protected by
push-to-reset mag-
netic-type circuit breakers . AC
circuit breakers are
denoted by a white
ring on the panel overlay . The
copilot's circuit breaker
panel also con-
tains
the AC BUS TIE circuit
breaker/switch which is
used to tie the L
AC
BUS and R AC BUS together
in the abnormal
situation of single
inverter
operation . Circuit breakers
are grouped together
into system
types (e .g .
ELECTRICAL, AFCS,
AVIONICS) .
PM-123

4-13
Change 2