F.
Manual Control Devices (Fig. 1 and Fig. 2)
(1)
Manual control devices are the GRD PWR switch on P5 panel and the GND SERVICE switch on the cargo door attendant's panel.
(a)
The GRD PWR switch is three-position, momentary, and spring-loaded to the center position. Setting the switch to ON opens GBs closes EPCs, and deactivates GROUND SERVICE switch. Setting the switch to OFF opens EPCs.
(b)
The GROUND SERVICE switch is two-position, solenoid-held to ON, and spring-loaded to OFF. Setting the switch to ON closes the ground service relay and activates the solenoid, holding the switch to ON. The switch cannot be held to ON if the GRD PWR switch is set to ON. Setting the switch to OFF opens the solenoid and ground service relay. The switch automatically trips to OFF when the BPP signals EPCs to close or when the EPCs close.
2. External Power Distribution (Fig. 1)___________________________
A. External power provides 115-volt, 3-phase, 400-Hz power to airplane power system when the GRD PWR switch is set to ON or to the ground service buses when the GROUND SERVICE switch is set to ON.
B. External power provides power directly to the lavatory mirror lights and the refueling power select relay R10. Relay, contactor, and switch settings do not control this power distribution.
(1)
Power to the lavatory mirror lights is from phase A of the external power receptacle.
(2)
Power to refueling power select relay is from the external power T-R and ground to the relay is from the BPP. When external power is connected to the receptacle and there are no faults, the relay is energized. The closed relay completes the circuit to power the fuel quantity gages and opens the battery charger mode control.
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A 737-300/400/500MAINTENANCE MANUAL
3. Operation (Fig. 2)
_________
A. Providing power to the external power receptacle illuminates the EXTERNAL POWER CONN and NOT IN USE lights on P19 panel and GND POWER AVAILABLE light on P5 panel. The EXTERNAL POWER CONN and GRD POWER AVAILABLE lights remain on at all times that external power is connected. The NOT IN USE light extinguishes when the GND PWR or GROUND SERVICE switch is set to ON or when the fueling station access door is opened.
B. Setting the GROUND SERVICE switch to ON energizes the ground service relay, which connects the 115-volt ac ground service bus to external power. This provides power to the battery charger, equipment cooling, service lights, and outlets. The GROUND SERVICE switch cannot be set to ON if the GRD PWR switch is set to ON or if external power is faulty.
C. Setting the GRD PWR switch and battery switch to ON closes the EPCs, which connect the airplane power system to external power. If the generator breakers are closed, they trip prior to the EPCs closing.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
AC EXTERNAL POWER - TROUBLE SHOOTING
____________________________________
1. General_______
A. These trouble-shooting procedures are necessary if incorrect indications show when you supply the external power.
B. The bus protection panel (BPP) monitors the voltage at the external power receptacle. If the voltage is incorrect, the BPP will not let you connect the external power source to the ac buses. Also, an incorrect voltage will cause the BPP to disconnect a defective source that is on the ac buses. These are incorrect voltages:
(1)
Undervoltage (UV) - less than 100 | 3 volts
(2)
Overvoltage (OV) - more than 130 | 3 volts
(3)
Negative Sequence Voltage (NSV) - the phase sequence is incorrect
2. The AC External Power Does Not Operate Correctly________________________________________________
A. Standard Tools and Equipment
(1)
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