H49849 H58376
115 Volt AC Power Distribution Diagram 507
24-51-0 Figure 2 (Sheet 2) Jun 20/83
Page 4
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
556 AC Power Distribution Component Location
Jun 20/83 Figure 3 24-51-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
28 VOLT AC POWER DISTRIBUTION - DESCRIPTION AND OPERATION
1. General
A. The 28-volt ac power used on the airplane is obtained from step down transformer type located at various points in the electrical system. Auto-transformers such as T36, T37, T38 and T52 (figure 1) have single phase, 115-volt, 400-cycle inputs with secondary taps of 24, 26, and 28 volts ac, depending on the application. The secondary taps on the auto-transformers are connected to 28 volts ac to buses which supply mostly lighting circuits. The X sections of both 3-phase, 115-volt ac bus No. 1 and 2 furnish 28-volt auto-transformers shown as single-phase main No. 1 and 2 single-phase, 28-volt transfer buses are fed from the 115-volt ac transfer buses No. 1 and 2.
B. Auto-transformers T36 and T37 supply 28-volt buses shown as single-phase main No. 1 and 2 respectively. (See figure 1.) The auto-transformers are fed by X sections of both 3-phase, 115-volt ac bus No. 1 and 2. The No. 1 and 2 single-phase, 28-volt transfer buses are fed from the 115-volt ac transfer buses No. 1 and 2 respectively. The current transformers and terminal strips which are related to a particular bus are located adjacent to connected components.
C. Single-phase ground service 28-volt ac transformers T3, T6 and T10 are fed from the 3-phase, 115-volt ac ground service bus phases A, B and C respectively and are located in junction box J4. The 28-volt main No. 1 transfer bus transformer T38 and the 28-volt main No. 1 bus transformer T36 shown on figure 1, are also in J4. Transformers T37 and T52, which are similar, but connected to No. 2 buses, are in junction box J5, along with cove lights 28-volt transformers T23 and T24. Junction boxes J4 and J5 are in the electronics equipment bay on the right-hand side. Control cabin lighting transformers T32, T33 and T34 are located in the space to the rear of panel P6-3.
500
May 15/67 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 24-52-0 Page 1
H21689 H21698
28 Volt AC Power Distribution Bus Diagram 500
24-52-0 Figure 1 May 15/67
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
500 28 Volt AC Power Component Location
May 15/67 Figure 2 24-52-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
STANDBY POWER SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
AT G-AVRL THRU G-BJCV CA B2501 THRU B2503 IDO 601 OI G-BGTW THRU G-BJBJ ZD CN-RMI THRU CN-RML
1. General
A. The standby system is used to supply power to essential ac and dc systems. Under normal conditions, the standby power switch is in the AUTO position, the standby ac bus is energized from the 115-volt ΦA transfer bus No. 1, and the standby dc bus is energized from the airplane dc bus No. 1. In the event of losing either the ac or dc normal power, the standby power transfer bus relay No. 1 (R36) is activated by the deactivation of the standby power transfer bus relay No. 2 (R37). This connects the dc standby bus to the battery bus and re-energizes the ac standby bus by activating the static inverter (Fig. 1).
B. During checkout of the system on the ground, or refueling the aircraft on battery power only, the standby system is activated by placing the standby power switch in the BATTERY position. This activates the power transfer bus relay No. 1 (R36), which connects the dc standby bus to the battery bus and the ac standby bus to the static inverter.
C. During electrical smoke isolation procedures, the standby system is deactivated by placing the standby power switch in the OFF position.
2. Operation
