C. Procedure
S 424-006
(1) Install the unit as follows:
(a)
Attach the unit to the P6 panel with four screws.
(b)
Connect the electrical connector to the unit.
(c)
Close the P6 panel.
D. Do a test of the unit installation.
S 844-013
(1)
Supply electrical power (AMM 24-22-00/201).
S 864-014
(2)
Make sure the EICAS system is operational (AMM 31-41-00/201).
S 864-015
(3)
Open the applicable P6 panel circuit breaker:
(a)
6M16 CAPT PRIM INSTR BUS A
(b)
6M22 F/O PRIM INSTR BUS A
S 754-016
(4)
Make sure the applicable EICAS status message, F/O INST XFER, CAPT INST XFER is shown on the display.
S 864-017
(5)
Close the applicable P6 panel circuit breaker.
(a)
6M16 CAPT PRIM INSTR BUS A
(b)
6M22 F/O PRIM INSTR BUS A
(6)
Make sure the EICAS status message is not shown on the display.
S 754-018
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MAINTENANCE MANUAL
S 844-019
(7) Remove electrical power if it is not necessary (AMM 24-22-00/201).
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28-VOLT AC POWER DISTRIBUTION - DESCRIPTION AND OPERATION
_________________________________________________________
1. General_______
A. The 28-volt AC system consists of three buses. These are: left 28-volt AC bus, right 28-volt AC bus, and the 28-volt AC ground service bus. System components are autotransformers.
2. Component Details (Fig. 1)_________________
A. Autotransformers
________________
(1) Autotransformers step down 115-volt single-phase AC power to 28-volt AC power. The left autotransformer is in misc. electrical equipment panel P70. The right autotransformer is in misc. electrical equipment panel P33. Circuit breakers for the left and right buses are in main power distribution panel P6 and in overhead circuit panel P11. The ground service autotransformer is in P34 panel. Ground service bus circuit breakers are on APU/external power panel P34.
3. Operation (Fig. 2)_________
A. Functional Description
______________________
(1)
Autotransformers receive input power from a single phase of the respective bus. A thermal circuit breaker in the primary of each autotransformer protects the autotransformer and wiring from excessive current.
(2)
Autotransformers for the left and right 28-volt AC buses are rated at 750-VA of power. The ground service autotransformer is rated at 2.5-KVA.
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MAINTENANCE MANUAL
MISCELLANEOUS ELECTRICAL EQUIPMENT PANEL, P70
28 Volt AC Power Distribution Component Location
Figure 1 (Sheet 1)
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