The AC electrical power distribution system allows for the distribution of AC power to the aircraft system from the different power sources: VFGs, APU GEN, EXT PWR, and RAT GEN. The system consists of the ACPC, CCBP and the EMS CDUs.

The distribution procedure includes:

• Automatic switching of circuits and sources
• Manual switching of circuits and sources
• Automatic detection and isolation of defective circuits
• Transmission of data to related systems and components.

The AC power center (ACPC) is the main component of the AC electrical load distribution system. The ACPC controls primary and secondary distribution of the AC electrical power to the aircraft.

The primary subassembly contains the components that control and switch the AC power input to the four main AC busses. The main AC busses supply AC power to the secondary power distribution subassembly. Each main AC bus is supplied at 26 KVA.The secondary subassembly supplies power to the secondary loads, electro-hydraulic pumps, passenger compartment feeders, and main feeders in the CCBP.

The control and logic subassembly monitors the status of the smart contactors, relays, and circuit breakers. Data from the control and logic subassembly is transmitted to the electrical management system control and display units (EMS CDUs). It is also sent to the central aircraft information maintenance system (CAIMS) for status and system tests.

The control and logic subassembly is the interface to the EMS for automatic or manual control of electrical power distribution and isolation of faults. Usual operation and emergency procedures are programmed into the software to automatically control the hardware components.

The CCBP is installed on the bulkhead behind the copilots seat. The CCBP gives protection and distributes power to AC and DC loads. It has the capacity to include 80 single-phase circuit breakers or a combination of three-phase and single-phase circuit breakers. The status of these circuit breakers is sent to the EMS CDUs through auxiliary contacts on each circuit breaker.

You can get the AC power source and AC electrical load isolation procedures from the EMS CDUs. The LRU tests are done through the interface with the EMS CDUs and the CAIMS. Built-in test (BIT) functions monitor the correct operation of the AC electrical load distribution system. Data on unsatisfactory conditions is kept in memory for LRU tests and corrections.

AC Power Center (ACPC)

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The ACPC controls and monitors the AC power system and supplies power to the circuit breakers on the cockpit circuit breaker panel (CCBP). The ACPC is installed above the floor in the baggage compartment.

The ACPC controls primary power and secondary distribution of the AC electrical power to the aircraft. For this function, it uses line contactors, transfer contactors, smart contactors, solid state power converters (SSPC), relays, circuit breakers, and current sensors. These LRUs are located in the three subassemblies that follows:

• The primary power switching subassembly installed in the bottom part of the ACPC
• The secondary power distribution subassembly installed in the top part of the ACPC
• The control and logic subassembly installed in the middle part of the ACPC

The ACPC sends current bus and contactor status data to the EMS CDUs. The ACPC receives bus isolation signals from the EMS CDUs. Data is sent along an RS422 data bus from the ACPC to the main generator control units (GCUs) and the APU GCU.

The ACPC has a built-in-test (BIT) to give system diagnostics and to identify component malfunctions. The BIT is a combination of hardware and software, and can identify a minimum of 95% of the functional malfunctions that affect the systems performance. The ACPC BIT detects and isolates system malfunctions at the line replaceable unit (LRU) level.

Primary Power Subassembly

The primary power subassembly is contained in the lower section of the ACPC and contains:

• Generator line contactors (GLC)
• Generator transfer contactors (GTC)
• APU/external power line contactor (APU/ EPLC)
• Line current transformer assemblies (LCTA)
• External AC TRU
• Electronic module 3 (EM 3)

It receives power from the four VFGs, APU generator or external power. Vertically the subassembly is divided by internal fire walls into four sections so that each section is physically isolated from the others. Starting from left to right, the sections are AC BUS 4, AC BUS 3, AC BUS 1 and AC BUS 2.

Generator Line Contactor (GLC)

There are four L-series generator line contactors (GLCs) located at the bottom of the primary power subassembly. They are a two-position contactor with 28 VDC coil and multiple auxiliary terminal. The GLCs are controlled by their respective GCU. When the contactors are energized (generator position), they allow the generator to supply its primary AC bus located in the ACPC. When deenergized (transfer position), they allow an alternate source (VFG, APU GEN, external AC) to supply the primary AC bus.

The four GLC labels and functions are as follows:

GLC labels and Functions

RELAY (LABEL)	FUNCTION
GLC 1 (K5)	Supply VFG 1 output to Primary AC Bus 1
GLC 2 (K7)	Supply VFG 2 output to Primary AC Bus 2
GLC 3 (K10)	Supply VFG 3 output to Primary AC Bus 3
GLC 4 (K13)	Supply VFG 4 output to Primary AC Bus 4

Generator Transfer Contactors

There are two types of generator transfer contactors (GTCs) that make up the AC distribution system. One type of GTC is a two position L-series contactor, the other is a three-position center-off terminals LC-series contactor with 28 VDC coil and multiple auxiliary terminal. The GTCs are configured by the primary logic cards to allow alternate power sources to feed the ACPC primary AC buses, in the event of a failed or unavailable generator.

The transfer contactor labels and types are as follows:

GTC Types and Labels

GTC	LABEL	TYPE
1 and 7	K4	3 Position
10 and 2	K6	3 Position
6 and 3	K9	3 Position
5 and 4	K12	3 Position
8	K3	2 Position
9	K2	2 Position
11	K11	2 Position
12	K8	2 Position

APU/External Power Line Contactor

The APU external power line contactor (APU/EPLC) is a three-position ZJC-series contactor, APU/OFF/EXT PWR. The contactor is a three-pole, double throw contactor with center off terminals, 28 VDC coil, and multiple auxiliary terminals. It is labeled K1 and is controlled by the primary logic cards when in the external power position, and by the APU GCU, when in the APU position. Either position provides power to the GTCs for system distribution. If neither system is on, the APU/EPLC goes to its center-off position.

Line Current Transformer Assembly (LCTA)

There are six line current transformer assemblies (LCTA) installed above the input terminal studs at the bottom of the ACPC primary power subassembly.

The three-phase line current transformer assemblies monitor the three phases of each AC generator including external AC power. From left to right the sources monitored are: VFG 4, VFG 3, VFG 1, VFG 2, APU GEN and External AC.

The analog signals from five of the LCTAs go to the generator control units (GCUs) to control the input from the main genrators and the APU generator. The analog signal from the last LCTA goes to the ACPC logic with the signal from the external power receptable current transformer.

All VFGs and APU LCTAs report to their respective GCUs. The external AC LCTA reports to the external power quality monitor located in the ACPC control and logic subassembly.

External AC TRU

The external AC TRU (EXT AC TRU) is comprised of three stepdown transformers and a rectifier assembly. The components of the EXT AC TRU are mounted immediately above the APU/EPLC. The EXT AC TRU receives external AC from the electronic module 3 (EM 3) and converts it to 28 VDC.

Electronic Module

Electronic module 3 (EM 3) is a small circuit card containing fuses. It taps off voltage from the ACPC external power input and sends it to the EPQM (via fuses for power quality) and to the EXT AC TRU (for 28 VDC conversion).

The Electronic modules do the functions that follow:

• Condition the core power and protect the load for the generator transfer contactors (GTCs) and the external power line contactors
• Protect the load for the ACPC control logic
• Monitor the protection devices

Y-series Relay (K28)

The Y-series relay (K28) in the ACPC is used to give the APU GLC status to the APU GCU. It is energized in parallel with K1 APULC coil from the APU GCU through the hard wired APU GLC Drive signal. The relay (K28) status (APU GLC STATUS) is sent back to the APU GCU to verify the command.

Secondary Power Subassembly

The secondary power subassembly makes up the top portion of the ACPC and contains:

• Thermal circuit breakers
• Two electronic modules
• Twenty four current sensor assemblies
• Four electric hydraulic pump contactors
• Four AC bus feed contactors
• Four cabin feed contactors

Vertically, the subassembly is divided into four sections so that each section is physically isolated from the other by internal firewalls. There is a separate component compartment for each main AC bus. Because of this, a main AC bus that has a malfunction cannot give malfunctions to the other main AC busses. Software does not control the primary AC power components. Starting from left to right, the sections are AC BUS 4, AC BUS 3, AC BUS 1 and AC BUS 2.

Thermal Circuit Breakers

The ACPC thermal circuit breakers are provided for circuits that do not require logic control. All thermal CBs have auxiliary contacts and are monitored by the secondary logic cards. The CBs status is redirected to the EMS CDUs, where it can be monitored by the crew, but they can not be pulled, set or reset from the EMS CDUs.

The ACPC can have up to 32 single-phase, or a combination of single and 3Ø circuit breakers. Each CB has an auxiliary lead that sends a status signal to the EMS CDU through an ARINC 429 bus. Under usual conditions, the CBs are set to IN. When a CB is open, the auxiliary lead sends an OUT signal. These CBs are part of the secondary distribution subassembly. The single-phase CBs can have a rating of 2.5 A, 5 A, or 7.5 A. The three-phase CBs can have a rating of 7.5 A or 15 A.

Some of the systems supplied by the breakers are, APU battery heater, APU battery charger EXT AC INTERLOCK, EMS CDU 1/2 PWR C, DCPC EXT CTL PWR, EXT AC PBA LTS, (AC 1, AC 2, AC 3 and AC 4) CABIN FEED and H STAB TRIM CH 1.

The ACPC includes the CBs that follow:

On A/C 9127 to 9169 for Global 5000 or On A/C 9003, 9004, 9025, 9052 to 9158 and Post SB 700-24-034 for Global Express and On A/C 9159 to 9169 for Global XRS:

SYSTEM	NAME	CB
Electrical Power	AC 1 CABIN FEED	B5
Electrical Power	AC 2 CABIN FEED	B8
Electrical Power	AC 3 CABIN FEED	B3
Electrical Power	AC 4 CABIN FEED	B1
Electrical Power	APU BATT CHGR	B7
Electrical Power	APU BATT HEAT	A1
Electrical Power	DCPC EXT CTL PWR	A11
Electrical Power	EMS CDU 1/2 PWR C	A10
Electrical Power	EXT AC INTERLOCK	A9
Electrical Power	EXT AC PBA LTS	A12
Electrical Power	SATCOM AMP	A14
Electrical Power	STAB TRIM CH1	B6

On A/C 9127 to 9999 for Global 5000 or On A/C 9002 to 9158 for Global Express and On A/C 9159 to 9999 for Global XRS:

SYSTEM	NAME	CB
Electrical Power	AC 1 CABIN FEED	B5
Electrical Power	AC 2 CABIN FEED	B8
Electrical Power	AC 2 CABIN FEED 2	A13
Electrical Power	AC 2 CABIN FEED 3	A15
Electrical Power	AC 2 CABIN FEED 4	C7
Electrical Power	AC 3 CABIN FEED	B3
Electrical Power	AC 3 CABIN FEED 2	B4
Electrical Power	AC 4 CABIN FEED	B1
Electrical Power	APU BATT CHGR	B7
Electrical Power	APU BATT HEAT	A1
Electrical Power	DCPC EXT CTL PWR	A11
Electrical Power	EMS CDU 1/2 PWR C	A10
Electrical Power	EXT AC INTERLOCK	A9
Electrical Power	EXT AC PBA LTS	A12
Electrical Power	SATCOM AMP	A14
Electrical Power	STAB TRIM CH1	B6

Electronic Modules

The secondary power assembly contains two electronic modules, EM 1 and EM 2. The electronic modules (EMs) incorporate fuses, diodes and resistors. The EMs receive 28 VDC from five different power sources, and redistribute it to the three ACPC internal power supplies (through fuses) and the contactor coils (through fuses and diodes).

The five power sources to the EMs are:

• DC BUS 1
• BATT BUS
• DC ESS BUS
• EXT AC TRU
• APU BATT DIR BUS

Current Sensors Assemblies

There are 24 current sensors installed in the ACPC secondary power subassembly.

The output of each phase for the electrical hydraulic pump and AC bus feed contactors are monitored by current sensors (ISA). The 24 sensors report to the secondary logic cards for system control and monitoring. Each main AC bus is monitored by 6 current sensors. The ACPC monitors the busses for over-current and energizes a transfer contactor to supply a bus from another bus if there is a malfunction. 

Electric Hydraulic Pump Contactors

The ACPC provides four contactors (also known as smart contactor) for control and protection of the four alternating current motor pump (ACMP). Each ACMP is powered from a different primary AC bus

The ACMP contactors are controlled and monitored by the secondary logic cards. The secondary logic cards also monitor the contactor position (auxiliary contact) and the output current using current sensors.

Using the EMS CDUs, the crew can monitor the contactor position and inhibits its operation. The EMS CDUs also receive discrete input from the ACMP switches (hydraulic control panel), which is forwarded to the secondary logic card along with the contactor inhibit command.

The secondary logic cards receive discrete inputs from the ACMP switches and digital signals from the EMS CDUs for control of the contactors.

AC Bus Feed Contactors

Four H-series AC bus feed contactors (smart contactor) are used to connect each primary AC bus to its respective cockpit circuit breaker panel (CCBP) secondary AC bus. These are a three-pole, double throw contactor with latch mechanism, 28 VDC coil, and multiple auxiliary terminals.

The AC bus feed contactors are controlled and monitored by the secondary logic cards. The secondary logic cards also monitor the contactor position (auxiliary contact) and the output current using current sensors.

Using the EMS CDUs, the crew can monitor the contactor position and inhibits its operation (isolate the selected secondary AC bus). The EMS CDUs communicate the inhibit selection to the secondary logic cards.

AC Bus Feed Contactors

CONTACTOR	FUNCTION
K15	Connects power from ACPC AC BUS 1 to CCBP AC BUS 1 A
K18	Connects power from ACPC AC BUS 2 to CCBP AC BUS 2 A
K21	Connects power from ACPC AC BUS 3 to CCBP AC BUS 3 A
K25	Connects power from ACPC AC BUS 4 to CCBP AC ESS BUS.

Cabin Feed Contactors

Four K-series cabin feed contactors (relays) are used to connect primary AC bus power, via circuit breakers, to cabin systems. These are a three-pole, double throw relay with latch mechanism, 28 VDC coil, and multiple auxiliary terminals. The cabin feed contactors are controlled and monitored by the secondary logic cards. They also monitor the contactor position (auxiliary contact) and EMS CDUs inhibit command. The EMS CDUs inhibit command is selected by the crew to isolate one or more of the cabin feeds.

AC Bus Feed Contactors

CONTACTOR	BUS SOURCE
K16	AC BUS 1 via CB-B5
K19	AC BUS 2 via CB-B8
K23	AC BUS 3 via CB-B3
K26	AC BUS 4 via CB-B1

Note:
The AC bus feed contactors and the electric hydraulic pump contactors are referred to as smart contactors.

The combination of the secondary logic cards, the current sensors and the contactors enable the AC distribution system to monitor and control the loads without the need of circuit breakers. This combination is also referred to as smart contactor control circuit

The secondary logic cards monitor the following:

• Voltage from the main AC buses
• Current from the current sensors
• Contactor position using status contacts on the contactors

If an overcurrent occurs, main AC bus voltage is missing, and/or the contactor does not respond to command, the secondary logic cards de-energize the affected contactors immediately.

Y-series Relay (K27)

The Y-series relay is a three pole, single throw, normally closed, latched 28 VDC single coil relay with auxiliary contacts. The Y-series relay (K27) is closed so that AC external power can supply the EMS CDU, DCPC, and ELECTRICAL control panel, while the BATT MSTR switch is not set to ON.

Control and Logic Subassembly

The control and logic subassembly controls the operation of the ACPC. The control and logic subassembly makes up the center portion of the ACPC and contains:

• Three primary logic cards
• Four secondary logic cards
• External power quality monitor
• External AC/DC converter
• Fifteen solid-state power controllers (SSPC)
• Two microprocessor cards
• One supervisor card
• Electromagnetic interference (EMI) gasket

It also contains the communication modules that permit communication on ARINC 429 and RS422 data busses, and discrete communication with the GCUs.

Primary Logic Cards

Three primary logic cards interface with the GCUs and the EPQM for AC power source availability as well as bus fault information. They also interface with the GTCs, the GLCs and the APU/EPLC for primary bus distribution (the GLCs are monitored and controlled by the GCUs but they are also monitored by the primary logic cards for distribution information). The primary logic cards work on a voting system where two cards must agree before an action is carried out. The distribution logic is built into each card, and primary distribution is carried out, even if ARINC 429 data bus communication is lost.

Secondary Logic Cards

Four secondary logic cards monitor and control the AC bus feed, the electric hydraulic pump (EHP) feed contactor and current sensor pairs for the respective AC BUS. Hardware based logic and two microprocessors do the management and control functions. The secondary logic controls data communication, solves boolean equations, and makes sure the essential loads are controlled. The combination of contactor, current sensor and control functions of the secondary logic card is referred to as a smart contactor.

The secondary logic cards interface with the external power quality monitor for secondary load control under external power conditions. The secondary logic cards are also the point of connection for the thermal circuit breaker status lines and the cockpit switches for the fuel and hydraulic pump associated with an AC bus. AC bus voltage sensing is also handled by the secondary logic cards.

External Power Quality Monitor

The external power quality monitor (EPQM) verifies the incoming external AC for valid power. Once all parameters are met, it allows the selection of the power source and signals the primary logic cards to energize the APU/EPLC for aircraft feed. If any faults should occur the EPQM disconnects the external power and the fault signal is transmitted to the EMS CDU.

If the power quality is not within the specified parameters, the ground unit connector is opened through the interlock signal on pin F, and the external source is disconnected.

The AC external power quality monitor continuously does a check of the AC external power parameters that follow:

• Undervoltage/overvoltage
• Underfrequency/overfrequency
• Feeder fault
• Open feeder
• Overcurrent
• Phase sequence
• Receptacle fault

External AC/DC Converter

The external AC/DC converter card (an analog to digital converter) is the connection point for all discrete and analog signals external to the ACPC associated with the APU battery, APU battery charger, and the APU start contactor assembly (ASCA). In addition, the external AC/DC converter houses one of three internal power supplies for the ACPC.

The AC/DC converter monitors the APU battery voltage and current, and sends this data to the EMS CDUs through an ARINC 429 bus.

Solid-State Power Controller (SSPC) Power Assembly

The 15 identical SSPC power assemblies provide control of AC subsystem loads (i.e.: fuel pump, landing lights etc.). Each power assembly accommodates three SSPCs for control and protection of three single-phase loads or one three phase load. Thus, up to a total of 45 single-phase loads are accommodated by these power assemblies. No more than one AC bus is connected to each SSPC power assembly.

Each SSPC power assembly is hard coded into the software and becomes programmed by the ACPC upon power-up to allow 2.5, 5.0, or 7.5 amp draw. Each SSPC power assembly is designed to provide the following:

• Circuit breaker function and status
• Logic equation switch
• Virtual switch
• Voltage monitoring
• Current monitoring

The SSPC power assembly provides the circuit breaker function for its associated load. All circuit breaker actions are controlled and/or monitored by the EMS CDU. The following are the SSPC power assembly status operations provided with this function:

• IN
• OUT
• TRIPPED
• LOCKED

The status information is displayed on the EMS CDU and on the portable maintenance access terminal (PMAT).

The logic equation switch is turned on based on the programmed logic in the SSPC. When external input is required for the logic equation (e.g. light switch in the ON position), this information is provided via the EMS CDU. The virtual switch, when used, is located on one of the three control pages in the EMS CDU. Most systems do not have the virtual switch option and this selection is always ON in the SSPC. Voltage and current monitoring status is available in the EMS CDU and the PMAT.

Each parameter is reported to the EMS CDU for CAIMS interface via the ARINC 429 data bus. They can be manually controlled, using the EMS CDU. Of the 15 power assemblies five are fed from AC bus 1, two from AC bus 2, two from AC bus 3, and six from AC bus 4.

If a SSPC power assembly is replaced or swapped, on power-up the ACPC will program the new assembly to meet the logic requirements of the position in which it is installed.

SSPC Power Sources

SSPC POWER ASSEMBLY	POWER SOURCE
SSPC Power Assemblies 1 thru 5	AC Bus 1
SSPC Power Assemblies 6 and 7	AC Bus 2
SSPC Power Assemblies 8 and 9	AC Bus 3
SSPC Power Assemblies 10 thru 15	AC Bus 4

Microprocessors

Two identical microprocessors are used in the ACPC. The cards have three functional blocks: a system power supply, an ARINC bus interface unit (BIU), and the microprocessor.

The power supply receives power from three primary DC buses (DC BUS 1, DC ESS BUS, BATT BUS) and external AC TRU to supply various levels of DC power (logic power, voltage references, etc.) for the internal use of ACPC circuits. The microprocessor power supplies and the one on the external AC/DC converter card, constitutes the three independent power supplies internal to the ACPC.

The microprocessors and gate arrays process data which is received in discrete and analogue inputs. Dual gate arrays monitor and process data from external sources for the control of essential electrical loads.

The microprocessors and the control logic gates are used for the functions that follow:

• Data transfer
• Boolean equation solutions
• Electrical load control
• Software control of circuits

The ARINC bus interface unit (BIU), which includes one ARINC 429 transmitter and two ARINC 429 receivers, handles all communication with the EMS CDUs.

The microprocessors supply the EMS CDUs with the AC bus data that follows:

• Power source
• Energized or de-energized
• Defective Manually isolated

The microprocessor, an Intel 80C186, handles all functions of the ACPC except primary power distribution. The microprocessor performs and gathers BIT and CAIMS information pertaining to the ACPC. Any system faults are recorded in the NVM and can be down loaded via CAIMS.

Supervisor

The supervisor monitors both microprocessors operations. It insures that both are in agreement with system status and condition. If a microprocessor should fail, the supervisor switches operating modes of the failed microprocessors from active to shadow. On system power-up, the left microprocessor is active by default, unless a fault is detected.

Personality Module

The supervisor also houses a personality module containing configuration information of optional and spare secondary loads in the aircraft. The personality module is not reprogrammable and contains the following load information:

• Names
• Ratings
• Populated/non-populated
• Aircraft configuration ID

Electromagnetic Interference Gasket

An electromagnetic interference (EMI) gasket is installed between the control and logic section and its cover. During removal of any logic circuit cards, the EMI gasket is inspected for damage thickness.

Note:
Replace gasket if it is damaged or compressed more than one third of its original thickness of 3.18 mm (0.125 in).

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The AC electrical power distribution system allows for the distribution of AC power to the aircraft system from the different power sources: VFGs, APU GEN, EXT PWR, and RAT GEN. The system consists of the ACPC, CCBP and the EMS CDUs.

The distribution procedure includes:

• Automatic switching of circuits and sources
• Manual switching of circuits and sources
• Automatic detection and isolation of defective circuits
• Transmission of data to related systems and components

The AC power center (ACPC) is the main component of the AC electrical load distribution system. The ACPC controls primary and secondary distribution of the AC electrical power to the aircraft.

The CCBP is installed on the bulkhead behind the copilots seat. The CCBP gives protection and distributes power to AC and DC loads. It has the capacity to include 80 single-phase circuit breakers or a combination of three-phase and single-phase circuit breakers. The status of these circuit breakers is sent to the EMS CDUs through auxiliary contacts on each circuit breaker.

The CCBP supplies 3-phase AC power from AC busses 1, 2, 3, and the AC essential (ESS) bus to TRU 1, ESS TRU 1, ESS TRU 2, and TRU 2 as follows:

• The CCBP AC bus 1 supplies power to the secondary loads. It also supplies power through CB G6 and the ETTC to the ESS TRU 1
  
  
• The CCBP AC bus 2 supplies power to the secondary loads and to TRU1 through CB A2
  
  
• The CCBP AC bus 3 supplies power to the secondary loads and to TRU2 through CB C2
  
  
• The CCBP ac ESS bus supplies power to ESS TRU 2 through CB E8. Also, the CCBP ac ESS bus can supply power to the ESS TRU 1 through CB E11 and the ETTC

You can get the AC power source and AC electrical load isolation procedures from the EMS CDUs. The LRU tests are done through the interface with the EMS CDUs and the CAIMS. Built-in test (BIT) functions monitor the correct operation of the AC electrical load distribution system. Data on unsatisfactory conditions is kept in memory for LRU tests and corrections.

The CCBP includes the AC CBs that follow:

On A/C 9127 to 9156 Pre SB 700-1A11-24-006 for Global 5000 and On A/C 9002 to 9156 Pre SB 700-24-065 for Global Express:

SYSTEM	NAME	CB
AFCS	A/T CTLR	H6
Air Conditioning	TRU BAY FAN	G12
Communications	SATCOM FREQ UNIT	H12
Electrical Power	AC BUS 4 MONITOR	F1
Electrical Power	AV BATT CHGR	C5
Electrical Power	AV BATT HEAT	D3
Electrical Power	ESS TRU 1	G6
Electrical Power	ESS TRU 1 ALT	E11
Electrical Power	ESS TRU 2	E8
Electrical Power	RAT V/F MONITOR	F2
Electrical Power	TRU 1	A2
Electrical Power	TRU 2	C2
Flight Controls	SLAT/FLAP PWR 1	G9
Flight Controls	SLAT/FLAP PWR 2	E2
Flight Controls	STAB TRIM CH 2	E5
Ice and Rain Protection	TAT HT 3	D4
Ice and Rain Protection	L AOA HEAT	F4
Ice and Rain Protection	L ICE DETECTOR	F7
Ice and Rain Protection	TAT HT 1	F3
Ice and Rain Protection	L WINDOW HEAT	F11
Ice and Rain Protection	L WSHLD HEAT 1	H10
Ice and Rain Protection	L WSHLD HEAT 2	H11
Ice and Rain Protection	PITOT 1 HT A	H7
Ice and Rain Protection	PITOT 1 HT B	F5
Ice and Rain Protection	PITOT 2 HT	B1
Ice and Rain Protection	PITOT 3 HT	F6
Ice and Rain Protection	R AOA HEAT A	H9
Ice and Rain Protection	R AOA HEAT B	F8
Ice and Rain Protection	R ICE DETECTOR	H8
Ice and Rain Protection	TAT HT 2	F9
Ice and Rain Protection	R WINDOW HEAT	B2
Ice and Rain Protection	R WSHLD HEAT 1	D5
Ice and Rain Protection	R WSHLD HEAT 2	D6
Ice and Rain Protection	STBY PITOT HT	F10

On Global XRS or On A/C 9157 and Subs and Post SB 700-1A11-24-006 for Global 5000 and On A/C 9157 to 9158 and Post SB 700-24-065 for Global Express:

SYSTEM	NAME	CB
AFCS	A/T CTLR	H6
Air Conditioning	TRU BAY FAN	G12
Communications	SATCOM FREQ UNIT	H12
Electrical Power	AC BUS 4 MONITOR	F1
Electrical Power	AV BATT CHGR	C5
Electrical Power	AV BATT HEAT	D3
Electrical Power	ESS TRU 1	G6
Electrical Power	ESS TRU 1 ALT	E11
Electrical Power	ESS TRU 2	E8
Electrical Power	RAT V/F MONITOR	F2
Electrical Power	TRU 1	A2
Electrical Power	TRU 2	C2
Flight Controls	SLAT/FLAP PWR 1	G9
Flight Controls	SLAT/FLAP PWR 2	E2
Flight Controls	STAB TRIM CH 2	E5
Ice and Rain Protection	TAT HT 3	D4
Ice and Rain Protection	L AOA HEAT	F4
Ice and Rain Protection	L ICE DETECTOR	F7
Ice and Rain Protection	TAT HT 1	F3
Ice and Rain Protection	L WINDOW HEAT	F11
Ice and Rain Protection	L WSHLD HEAT 1	H10
Ice and Rain Protection	L WSHLD HEAT 2	H11
Ice and Rain Protection	PITOT 1 HT A	H7
Ice and Rain Protection	PITOT 1 HT B	F5
Ice and Rain Protection	PITOT 2 HT	B1
Ice and Rain Protection	PITOT 3 HT	F6
Ice and Rain Protection	R AOA HEAT A	H9
Ice and Rain Protection	R AOA HEAT B	F8
Ice and Rain Protection	R ICE DETECTOR	H8
Ice and Rain Protection	TAT HT 2	F9
Ice and Rain Protection	R WINDOW HEAT	B2
Ice and Rain Protection	R WSHLD HEAT 1	D5
Ice and Rain Protection	R WSHLD HEAT 2	D6
Ice and Rain Protection	STBY PITOT HT	F10
Ice and Rain Protection	EVS FAIRING HEAT	G3
Ice and Rain Protection	EVS WINDOW HEAT	H5

AC Power Center (ACPC)

H-Series Contactors

The CCBP contains the three H-series contactors that follow:

• The RATLC (K3) is used to connect the AC ESS bus from the AC bus 4 to the RAT generator. This occurs when all usual AC power sources are lost. The position of this contactor is identified as K3
  
  
• The ETTC (K2) is used to supply the ESS TRU 1 bus from the AC bus 1 or from the AC ESS bus under RAT power conditions. The position of this contactor is identified as K2
  
  
• The AC bus 3 contactor (K1) is used to shed the secondary loads from the AC bus 3 when ground service mode is selected from the aft service control panel. This contactor is controlled by the DCPC

During usual conditions, the coil of the RATLC is not energized and the power from AC bus 4 is supplied to the AC ESS bus. If the RAT generator is the only source of AC power on the aircraft, the coil of the RATLC is energized by the RAT generator control unit (GCU) and the RAT generator supplies power to the AC ESS bus.

During usual conditions, the coil of the ETTC is not energized and the power from AC bus 1 is supplied to the ESS TRU 1. If the power from AC bus 1 becomes unsatisfactory, the coil of the ETTC is energized by the DCPC and the AC ESS bus supplies power to ESS TRU 1.

The ground load shedding line contactor (K1) is installed between AC bus 3 and the CBs for which it is not necessary to supply power to during ground service conditions. This contactor is closed during usual conditions and is controlled by the DCPC.

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Primary AC Distribution

Bus distribution for the AC system is contained in two areas, the AC power center (ACPC) and the cockpit circuit breaker panel (CCBP). The ACPC receives power from the VFGs, the APU generator and AC external power. Inside the ACPC are: AC bus 1, AC bus 2, AC bus 3 and AC bus 4. Inside the CCBP are AC bus 1A, AC bus 2A, and AC bus 3A and the AC essential bus. The ACPC AC buses 1, 2, 3 and 4 via AC bus feed contactors directly feed the CCBP AC buses.

Power sources are never paralleled on a bus. Each bus is normally fed from its own generator via a GLC. Any one generator can power two buses, if required, via its GLC and GTCs. Buses are physically and electrically separated from each other so a fault on one will not affect another. If a bus were to develop a bus fault, the GCU will disconnect the generator from its own bus by de-energizing its GLC. It will maintain generator excitation so that the generator can still be available to power other ACPC primary buses. ACPC bus distribution logic is controlled by the primary logic cards located in the ACPC control and logic subassembly. Switching actions are performed so as to limit power interruptions to 50 milliseconds or less.

One VFG can power a maximum of two AC buses. In the event of only one VFG being available, AC bus 1 and 4 have priority. For example, if only VFG 3 is powering the AC system, AC bus 1 and 4 will be powered, AC bus 2 and 3 will be load shed. If AC bus 1 or 4 lose their normal generator source, (i.e. VFG 1 or 4) it will be powered by the generator in the same position on the opposite engine. If that generator is not available, it will be powered by the other generator on the opposite engine. If that is also unavailable, the next choices would be the other generator on its own engine, followed by the APU generator or external AC power.

The APU generator power distribution will be discussed in the auxiliary AC power distribution section. The switching logic for AC bus 2 and 3 is similar to 1 and 4 with one exception. If its own generator is not available, the bus will be powered by the generator in the same position on the opposite engine. If that is not available, it will receive power from the other generator on the opposite engine. The last available source is either APU or external AC power, with the priority going to the APU. Neither AC bus 2 or 3 can be powered by the other generator on its own engine. If generators are not available on opposite engine than this means that the outboard generator on same engine is only one available and AC bus 1 and 4 have priority.

Bus Fault Protection

The GCU monitors generator loads for current draw. If the GCU senses an over current, the generator line contactor, for that bus, is de-energized to the off position and the ACPC is informed by the GCU. The ACPC then configures the generator transfer contactors to isolate the bus.

Communications

The ACPC sends data relevant to bus and contactor status to the EMS CDU on an ARINC 429 data bus. Transmitted data includes: EXT power status, bus logic status, bus source connections and faults. The EMS CDU communicates relevant data to the DAU for synoptic, CAS and CAIMS purposes. The ACPC also communicates with the five GCUs, transmitting data every 250 ms and receiving a response from each GCU within 50 ms.

 

POWER SOURCE (S) AVAILABLE	AC BUS 1 PWR SOURCE	AC BUS 2 PWR SOURCE	AC BUS 3 PWR SOURCE	AC BUS 4 PWR SOURCE
VFG 1,2,3 & 4	VFG 1	VFG 2	VFG 3	VFG 4
VFG 1,2 & 3	VFG 1	VFG 2	VFG 3	VFG 1
VFG 1,2 & 4	VFG 1	VFG 2	VFG 2	VFG 4
VFG 1,3 & 4	VFG 1	VFG 3	VFG 3	VFG 4
VFG 2,3 & 4	VFG 4	VFG 2	VFG 3	VFG 4
VFG 1 & 2	VFG 1	VFG 2	VFG 2	VFG 1
VFG 1 & 3	VFG 1	VFG 3	VFG 3	VFG 1
VFG 1 & 4	VFG 1	VFG 4	VFG 1	VFG 4
VFG 2 & 3	VFG 3	VFG 2	VFG 3	VFG 2
VFG 2 & 4	VFG 4	VFG 2	VFG 2	VFG 4
VFG 3 & 4	VFG 4	VFG 3	VFG 3	VFG 4
VFG 1	VFG 1	SHED	SHED	VFG 1
VFG 2	VFG 2	SHED	SHED	VFG 2
VFG 3	VFG 3	SHED	SHED	VFG 3
VFG 4	VFG 4	SHED	SHED	VFG 4
VFG 1 & APU	VFG 1	APU	APU	VFG 1
VFG 2 & APU	VFG 2	VFG 2	APU	APU
VFG 3 & APU	APU	APU	VFG 3	VFG 3
VFG 4 & APU	VFG 4	APU	APU	VFG 4
APU GRD *	APU	APU	APU	APU
APU FLT	APU	SHED	SHED	APU
VFG 1 & EXT	VFG 1	EXT	EXT	VFG 1
VFG 2 & EXT	VFG 2	VFG 2	EXT	EXT
VFG 3 & EXT	EXT	EXT	VFG 3	VFG 3
VFG 4 & EXT	VFG 4	EXT	EXT	VFG 4
EXT **	EXT	EXT	EXT	EXT
* Some loads will be shed with only APU power feeding, e.g. only one AC Hydraulic Pump can function at a time.
** External AC can be provided with aircraft on (or off...) jacks.

Secondary AC Distribution

The ACPC includes four secondary logic cards for control and protection of the main AC distribution feeders which are routed to the CCBP and for the four main electro-hydraulic pump feeders.

Secondary Logic Card Associations

	AC BUS 1	AC BUS 2	AC BUS 3	AC BUS 4
HYD Pump	3B (K14)	2B (K17)	1B (K20)	3A (K24)
AC BUS FEED	1A (K15)	2A (K18)	3A (K21)	AC ESS (K25)
AC CABIN FEED	1 (K16)	2 (K19)	3 (K23)	4 (K26)
FUEL Pump Switch	L AFT	L FWD	R FWD	R AFT
CB Status	AC 1 CABIN FEEDEMS CDU 1/2 PWRC EXT AC INTER LOCK EXT AC PBA LTS DCPC EXT CTL PWRSTAB TRIM CH 1	AC 2 CABIN FEED APU BATT CHGR SATCOM AMP	AC 3 CABIN FEED	AC 4 CABIN FEEDAPU BATT HEAT

Smart Contactors

The secondary logic cards provide a control and monitor function for two contactors (hydraulic pump and AC bus feed) in the secondary power subassembly of the ACPC. Bus power is routed to each contactor. The secondary logic cards control power to the coil. The output of each contactor is fed through three current sensors. The signals generated by the current sensors are routed back to the secondary logic card. The low-level AC signals are conditioned and then converted from an analog to a digital signal. The secondary logic card monitors the signal and, if the signal exceeds a set time/current characteristic, the contactor coil drive power is removed and a TRIP indication is transmitted to the EMS CDU for display next to the corresponding load name. Resetting the TRIP indication to IN on the EMS CDU will instruct the secondary logic card to provide coil power to close the contactor and again monitor the load current.

Solid-State Power Controller (SSPC) Cards

Each card holds three separate SSPC devices. The SSPC cards inside the ACPC are identical and are interchangeable with each other. Each card is associated with one AC bus. Each SSPC connected to one of the three phases, i.e. one SSPC per phase.

The SSPC normally acts as a single-phase load but can be programmed so that all three SSPCs on a card provide the function of a three-phase CB.

The rating of the each SSPC is established by the microprocessor at power-up and set to a value of either 2.5, 5, 7.5, 10, or 15 amps. The placement of the card and the designated settings inside the microprocessor software will program the rating and operation (either single phase or three phase) of each SSPC.

Logic associated with any load controlled by an SSPC is handled completely by the microprocessor. The SSPC will switch power to a load and provide a protective circuit breaker function. The microprocessor handles the responsibility of sending the ON or OFF command to the SSPC per the logic requirement of the load supplied by that SSPC.

There are 15 SSPC cards inside the ACPC. The load associated with each SSPC on a card is listed in the table below.

SLOT #	CARD NAME	PURPOSE	PWR SOURCE	SL0T #	CARD NAME	PURPOSE	PWR SOURCE
15	SSPC # 8	R FWD PRI PUMP	Ext A/D Conv.	14	SSPC # 7	AFT TANK L PUMP	Ext A/D Conv.
16	SSPC # 9	AFT TANK R PUMP	L µ P	13	SSPC # 6	L FWD PRI PUMP	L µ P
17	Secondary Logic Card	AC BUS 3 Related	L µ P	12	Secondary Logic Card	AC BUS 2 Related	R µ P
18	Primary Logic Card # 1		L µ P	11	EXT PWR QUAL MON		Ext A/D Conv.
19	SUPERVISOR		L/R µ P	10	R Microprocessor	Copilots EMS CDU
20	L Microprocessor	Pilots EMS CDU		9	EXT A/D CONV
21	Primary Logic Card # 3		R µ P	8	Primary Logic Card # 2		Ext A/D Conv.
22	Secondary Logic Card	AC BUS 4 Related	L µ P	7	Secondary Logic Card	AC BUS 1 Related	Ext A/D Conv.
23	SSPC # 10	R AFT PRI PUMP	R µ P	6	SSPC # 5	L RECIRC FAN	R µ P
24	SSPC # 11	R CTR XFER PUMP	R µ P	5	SSPC # 4	SPARE/SPARE/SPARE	R µ P
25	SSPC # 12	R WING LDG LT/R TAXI LT/APU OIL HEAT	Ext A/D Conv.	4	SSPC # 3	L WING LDG LT/L TAXI LT/SPARE	Ext A/D Conv.
26	SSPC # 13	R RECIRC FAN	Ext A/D Conv.	3	SSPC # 2	L CTR XFER PUMP	Ext A/D Conv.
27	SSPC # 14	SAT COM HPA FAN	L µ P	2	SSPC # 1	L AFT PRI PUMP	L µ P
28	SSPC # 15	AVIONICS FAN	L µ P	1
AC Logic Center Power Source Legend: L P = left microprocessor, R P = right microprocessor and Ext A/D Conv. (converter)

Cockpit Circuit Breaker Panel (CCBP) Distribution

The CCBP buses receive power from the ACPC primary buses. Each CCBP bus can only be fed from its associated ACPC bus. The AC power outputs to the transformer rectifier units (TRUs) are connected to the output side of the CBs. All other interfaces with the CCBP are made by the seven connectors (P1 through P7) for secondary load outputs and discrete inputs and outputs.

If the ACPC bus should become unpowered, the CCBP bus will also be unpowered with the exception of the AC essential bus (which can also be powered from the RAT generator). For this reason the CCBP buses are called feeder bus and given the suffix of A to the bus name (i.e. AC bus 1A). AC distribution from the ACPC to the CCBP is controlled by the secondary logic cards.

The cockpit circuit breaker buses feed subsystems via single or 3 Ø thermal circuit breakers.

The CCBP thermal circuit breakers have auxiliary contact for monitoring purposes. All the CBs auxiliary contacts report directly to the EMS CDUs, where the crew can monitor the CB status (IN, OUT, TRIP). During usual conditions, the CBs are closed. If the CB is opened automatically or manually, a signal is sent to the EMS CDUs.

The five TRU CBs have dual auxiliary contacts, one contact report to the EMS CDU and the second to the DCPC. The CB status to the DCPC is used for its internal control logic.

Power sources from the ACPC to the CCBP are as follows:

CCBP Power Source

CCBP	ACPC FEED & CONTACTOR
AC Bus 1A	AC Bus 1 via contactor K15
AC Bus 2A	AC Bus 2 via contactor K18
AC Bus 3A	AC Bus 3 via contactor K21
AC Essential Bus	AC Bus 4 via contactor K25 & RAT Generator Line Contactor K3. When the RAT contactor is energized power is routed directly from the RAT generator disconnecting the ACPC feed.

AC Bus 1A

INTERCONNECTION	SUBSYSTEM
CB-G6 (3 phase), ESS TRU Tie Contactor (K2)	ESS TRU 1
CB-G9 (3 phase)	SLAT/FLAP PWR 1
CB-H8 (single phase)	R ICE DETECTOR
CB-H7 (single phase)	PITOT 1 HT A
CB-H9 (single phase)	R AOA HEAT A
CB-H10 (single phase)	L WSHLD HEAT 1
CB-H11 (single phase)	L WSHLD HEAT 2
CB-H12 (single phase)	SATCOM FREQ UNIT

AC Bus 2A

INTERCONNECTION	SUBSYSTEM
CB-A2 (3 phase)	TRU 1
CB-G12 (3 phase)	TRU BAY FAN
CB-B2	R WINDOW HEAT
CB-B1	PITOT 2 HEAT

AC Bus 3A

INTERCONNECTION	SUBSYSTEM
CB C2 (3 phase)	TRU 2
CB C5 (3 phase)	AV BATT CHGR
CB D3 (single phase)	AV BATT HEAT
AC Bus 3 Shed relay K1, CB D4 (single phase)	TAT HEAT 3
AC Bus 3 Shed relay K1, CB D5 (single phase)	R WSHLD HEAT 1
AC Bus 3 Shed relay K1, CB D6 (single phase)	R WSHLD HEAT 2
CB-D10 (single phase)	AV BATT STBY ADI

AC Essential Bus

INTERCONNECTION	SUBSYSTEM
CB-E8 (3 Phase)	ESS TRU 2
CB-E11(3 Phase), ESS TRU Tie Contactor (K2)	ESS TRU 1 ALT
CB-F2 (single phase)	RAT V/F MONITOR
CB-E5 (3 phase)	STAB TRIM CH 2
CB-E2 (3 phase)	SLAT/FLAP PWR 2
CB-F7 (single phase)	L ICE DETECTOR
CB-F3 (single phase)	TAT HT 1
CB-F4 (single phase)	L AOA HEAT
CB-F5 (single phase)	PITOT 1 HT B
CB-F6 (single phase)	PITOT 3 HT
CB-F8 (single phase)	R AOA HEAT B
CB-F9 (single phase)	TAT HT 2
CB-F10 (single phase)	STBY PITOT HT
CB-F11 (single phase)	L WINDOW HEAT

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
A54	AC POWER CENTER (ACPC)	ZONE(S) 252	24-51-00 [ GX ] [ GXRS ] [ G5000 ]
A35	COCKPIT CIRCUIT-BREAKER PANEL	ZONE(S) 222	31-17-00 [ GX ] [ GXRS ] [ G5000 ]

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