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Power for the Essential AC bus is normally supplied by from the Left or
Right Main AC buses. Should a failure of all three primary power sources
(left, right and APU alternators) occur, the E-inverter will automatically
receive 28 VDC power from the Essential DC bus. The E-inverter in turn
will automatically supply single-phase (Phase A only), 115 VAC, 400 Hz
power to the Essential AC bus. The E-inverter can also be powered by the
Standby Electrical Power system (commonly referred to as the ABEX
generator) by manual selection as shown in Figure 4.
E-inverter operation is accomplished by ESS switchlight selection and
verified by observing the VOLTS and FREQ meters. The ESS switchlight is
located immediately below the BATTERY 2 CHGR FAIL annunciator on the
EPMP (Figure 6 Sheet 1). Illumination of the amber ESS AC BUS E INV
switchlight (AC POWER CONTROL section of the EPMP, Figure 6 Sheet 4)
indicates a request for service only, not actual E-inverter operation.
F. Power Distribution Box:
The Power Distribution Box (PDB), located in the right avionics rack, is the
load center of the electrical system. It serves as the terminal for all input
power and output to the buses and other loads in the aircraft. Located on
the front surface of the PDB are the load center circuit breakers, each
protecting a separate channel of power.
G. AC External Power System:
The AC power system includes provisions for connecting an external
source of regulated, three-phase, 115/200V AC, 400 Hz power. An external
AC power receptacle (Figure 9) is located forward of the tail compartment
door on the exterior of fuselage. With an external AC power supply
connected and operating, a blue AC EXT PWR annunciator (Figure 10) on
the overhead annunciator panel illuminates, indicating that external AC
power is available. Selecting the AUX PWR switch and at least one BATT
switch to ON (both shown in Figure 6 Sheet 8) will close the appropriate
relays to energize the AC buses. The TRU will then be activated to power
the DC buses.
If the main aircraft batteries are discharged or removed, a BATTERY
OVERRIDE SWITCH, located within the external AC receptacle, may be
used to initiate connection of AC external power by routing AC external
power (Phase A) directly to the ACBPCU. The ACBPCU then changes this
voltage to DC and routes it to the AUX PWR switchlight. When connection
is made through switch selection, the circuit from the ACBPCU holds the
power until disconnect is selected. Circuit protection from improper AC
external power is also provided by the ACBPCU.
OPERATING MANUAL
2A-24-00 PRODUCTION AIRCRAFT SYSTEMS
Page 10
May 30/02
Revision 7
H. APU AC Power System:
The APU alternator supplies AC power be distributed for electrical system
use. With the APU operating and the APU generator ready, a blue ALTNR
OFF annunciator on the APU control panel (Figure 11) is illuminated and a
blue APU ALT OFF message is displayed on CAS. Depressing the AUX
PWR switchlight on the EPMP (Figure 6 Sheet 8) routes APU alternator
power to the AC buses and the annunciations are removed.
I. Standby Electrical Power System:
The Standby Electrical Power system consists of a hydraulic motor-driven
generator and a Generator Control Unit (GCU). When no AC power is
available from either main AC bus or the auxiliary power source, Phase A of
the Essential AC bus and the Essential DC bus can receive power from this
system.
The Standby Electrical Power system serves to permit continued flight at
cruise altitudes after a double alternator/converter failure in order spare
heavy loads from the main aircraft batteries. Upon descent through
maximum APU starting altitude, the Standby Electrical Power system is
normally replaced with APU alternator power (AUX PWR). Although the
Standby Electrical Power system is not intended for use during approach
and landing (as demands on the hydraulic system could cause it to drop off
line), it may be used according to the limitations provided in the latest
approved revision of the GIV Airplane Flight Manual. Also, battery charging
when using the Standby Electrical Power system is not possible.
The constant-speed hydraulic motor-driven generator, located in the main
wheel well, is commonly referred to as the ABEX generator. The hydraulic
motor receives power from Combined hydraulic system pressure through a
normally open shutoff valve. With Essential DC bus power available, the
shutoff valve is energized closed. Loss of Essential DC bus power allows
the valve to open, allowing approximately 1,000 psi of Combined hydraulic
system pressure to spin up the motor-generator to its GCU-regulated
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湾流4操作手册 Gulfstream IV Operating Manual 1(66)
