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POWER FAIL message displayed on CAS. This message is displayed
whenever output power from the APU has dropped off line. If the APU
alternator is running and the AUX PWR switch is ON, a blue ALTNTR OFF
light located on the APU control panel (Figure 11) will be illuminated. A blue
APU ALT OFF message will be displayed on CAS if the APU alternator is
otherwise operational but has not been selected for use through the AUX
PWR switch.
An amber APU ALT HOT message will be displayed on CAS when the APU
alternator temperature exceeds 300° F (149° C).
C. Converters:
Two 30 kVA solid state converters are installed in the tail compartment: one
to protect and control each engine-driven alternator. Each converter
rectifies the AC alternator output into DC voltage, then converts it to 23 kVA
of 115/200V AC, 400 Hz, three-phase power. In addition, the converters
provide 250 amperes of DC power output regulated to 28 VDC. The output
of the APU alternator does not require a converter since its frequency is
fixed due to APU speed control.
Each converter contains extensive protection and fault sensing circuitry for
the engine-driven alternator and AC power system. Among the anomalies
OPERATING MANUAL
2A-24-00 PRODUCTION AIRCRAFT SYSTEMS
Page 8
May 30/02
Revision 7
for which protection is provided are:
• AC Bus Faults
• Alternator Underspeed, Overfrequency, Underfrequency and
Overvoltage
• Failed Converter Fans and Converter Overtemperature
• Converter Overvoltage, Undervoltage and Overcurrent
Normally, five high speed fans provide forced cooling air for each
converter. If one of the five cooling fans should fail, an amber L-R CONV
FAN FAIL message is displayed on CAS and the normally gray/black
FAILED FAN flag (on the converter itself, shown in Figure 8) changes to
white/black. These annunciations indicate the converter is operating ″on
condition″ and further actions shall be with reference to the latest approved
revision of the GIV Airplane Flight Manual. This is because if a second fan
should fail, related CAS message(s) may be cleared, leading the flight crew
to believe that the problem has corrected itself when, in fact, automatic
converter shutdown may occur. With ASC 285 incorporated, all messages
will remain illuminated.
When a converter exceeds 220° F (104° C), an amber L-R CONV HOT
message is displayed on CAS. Continued operation with an overheated
converter could result in automatic converter shutdown. The L-R CONV
HOT message will clear when converter temperature falls to 190° F (88° C)
and below.
An amber L-R AC POWER FAIL or L-R DC POWER FAIL message will be
displayed on CAS if AC output from the converter drops off line.
D. AC Bus Power Control Unit:
The AC Bus Power Control Unit (ACBPCU), located in the right avionics
rack, controls the connection of the AC power sources to the AC buses. By
providing automatic control capability over the AC power relays and
contactors, it controls the AC buses by switching AC bus power to an
alternate source should a malfunction occur. Manual control over the relays
and contactors is also available through the ACBPCU.
The ACBPCU provides electrical fault protection for the APU alternator,
external AC power system and AC buses. It protects the APU alternator
against overvoltage, undervoltage, undercurrent, underspeed and feeder
faults. External power protection includes overvoltage, undervoltage,
overfrequency, underfrequency, phase rotation, overcurrent and feeder
fault protection. The AC buses are protected against overcurrent,
undervoltage and feeder faults.
The ACBPCU provides regulation and excitation for the APU alternator. It
also provides 28V DC (through an internal TRU) for the dead battery
switch.
E. Emergency Inverter:
An Emergency Inverter (commonly referred to as the E-inverter) is installed
under the forward floor. In the event of Essential AC bus failure, it provides
power to Phase A of the Essential AC bus. Considered primarily an
emergency power source, sufficient power is supplied to operate only
equipment regarded as essential for flight. Among the items available:
• Bleed Air Isolation Shutoff Valve
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-24-00
Page 9
May 30/02
Revision 7
• Cabin Pressurization
• Cockpit Voice Recorder
• Electric Pitch Trim
• Engine Pressure Ratio
• Engine Oil Pressure
• Pitot Heat: Left and Standby
• No. 1 and No. 2 26V AC Transformers
• Power Lever Angle
• Temperature Control System
　
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