Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
42 Cards in this Set
- Front
- Back
|
The two basic principals for the 737 electrical system
|
• There is no paralleling of the AC sources of power.
• The source of power being connected to a transfer bus automatically disconnects an existing source. FM 6.60.10.1 - 20 DEC 13 |
|
|
What are the three main divisions of the electrical power system?
|
- The AC power system.
- The DC power system. - The Standby power system. FM 6.60.10.1 - 20 DEC 13 |
|
|
What is the primary source of electrical power?
|
Two engine driven IDGs.
FM 6.60.10.1 - 20 DEC 13 |
|
|
APU generator capabilities:
|
The APU generator can supply power to both AC transfer busses on the ground
or in flight. As the only power source, the APU generator can meet electrical power requirements for all ground conditions and most flight conditions. FM 6.60.10.1 - 20 DEC 13 |
|
|
External Ground Power capabilities:
|
When connected, external power can
supply power to both transfer busses. FM 6.60.10.1 - 20 DEC 13 |
|
|
What are the components of each AC power system?
|
- 1 transfer bus.
- 1 main bus. - 2 galley busses. - 1 ground service bus. FM 6.60.10.3 - 20 DEC 13 |
|
|
What additional component does Transfer Bus 1 power?
|
AC standby bus.
FM 6.60.10.3 - 20 DEC 13 |
|
|
What occurs if the AC source powering either transfer bus fails or is disconnected?
|
The transfer bus can be powered by any available source through the tie bus with
the bus tie breakers (BTBs). FM 6.60.10.3 - 20 DEC 13 |
|
|
Is it possible to power one transfer bus with external
power and one transfer bus with APU power? |
No.
FM 6.60.10.3 - 20 DEC 13 |
|
|
What happens when external power or APU is powering both transfer busses, and engine generator power is applied to its onside transfer bus?
|
External power or APU continues to supply power to the remaining transfer bus.
FM 6.60.10.3 - 20 DEC 13 |
|
|
In flight, what occurs if an engine generator is no longer supplying power to its own transfer bus?
|
The bus tie breakers automatically close to allow the other engine generator to supply both transfer busses through the tie bus and bus tie breakers.
FM 6.60.10.3 - 20 DEC 13 |
|
|
Describe the automatic generator on-online feature.
|
If the aircraft takes off with the APU powering both transfer busses, and the APU is either shut down or fails, the engine generators are automatically connected to their related transfer busses. This action occurs only once in flight and only under
the circumstances described above. FM 6.60.10.3 - 20 DEC 13 |
|
|
Describe automatic operation of the Bus Transfer System.
|
Either generator or the APU can supply power to both transfer busses. If the
BUS TRANS switch is in the AUTO position and the source powering the transfer bus is disconnected or fails, the source powering the opposite transfer bus automatically picks up the unpowered transfer bus through the bus tie breakers. FM 6.60.10.3 - 20 DEC 13 |
|
|
Describe the automatic load shedding feature which occurs during single engine driven generator operation.
|
Based on actual load sensing, the galleys and main bus on transfer bus 2 are shed first; if an overload is still sensed, the galleys and main bus on ransfer bus 1 are shed; if overload still exists, the in flight entertainment (IFE) buses are shed. When configuration changes to more source capacity (two generator operation), automatic load restoration of the main busses, galley
busses, and IFE buses occurs; manual restoration of galley and main bus power can be attempted by moving the CAB/UTIL power switch to OFF, then back ON. FM 6.60.10.3 - 20 DEC 13 |
|
|
Describe the APU automatic load shedding feature.
|
In flight, if the APU is the only source of electrical power, all galley busses and main buses are automatically shed. If electrical load still exceeds design limits, both IFE busses are also automatically shed. On the ground, the APU attempts to carry a full electrical load. If an overload condition is sensed, the APU sheds
galley busses and main busses until the load is within limits. Manual restoration of galley and main bus power can be attempted by moving the CAB/UTIL power switch to OFF, then back ON. FM 6.60.10.4 - 20 DEC 13 |
|
|
The generator drive (DRIVE) amber caution light is illuminated when:
|
Low oil pressure is sensed in the IDG.
FM 6.60.10.6 - 20 DEC 13 |
|
|
IDG low oil pressure is caused by one of the following:
|
• IDG failure
• Engine shutdown • IDG automatic disconnect due to high oil temperature • IDG disconnected through generator drive DISCONNECT switch FM 6.60.10.6 - 20 DEC 13 |
|
|
What is the purpose of the generator drive disconnect switch?
|
Disconnects the generator from the engine in the event of a generator drive malfunction.
Reactivation of the generator may be accomplished only on the ground by maintenance personnel. FM 6.60.10.6 - 20 DEC 13 |
|
|
What supplies 28 VDC power?
|
Three TR units, which are energized from the
AC transfer busses. 6.60.10.8 - 20 DEC 13 |
|
|
What is the primary purpose of the battery?
|
The battery provides DC power to loads required to be
operative when no other source is available. Battery start for APU. 6.60.10.8 - 20 DEC 13 |
|
|
amber ELEC light
|
On the ground, indicates that a fault exists in the DC power system or standby power system.
The ELEC light is inhibited in flight. 6.60.10.8 - 20 DEC 13 |
|
|
What is the function of the TRs?
|
The TRs convert 115 volt AC to 28 volt DC, and are identified as TR1, TR2, and TR3.
6.60.10.8 - 20 DEC 13 |
|
|
How is each TR powered?
|
TR1 receives AC power from transfer bus 1.
TR2 receives AC power from transfer bus 2. TR3 normally receives AC power from transfer bus 2 and has a backup source of AC power from transfer bus 1. 6.60.10.8 - 20 DEC 13 |
|
|
What is the minimum number of TRs required to supply the normal total connected DC load?
|
Any two TRs are capable
of supplying the total connected load. 6.60.10.8 - 20 DEC 13 |
|
|
What is the normal DC bus/power configuration?
|
DC bus 1, DC bus 2, and the DC standby bus are
connected via the cross bus tie relay. In this condition, TR1, and TR2 are each powering DC bus 1, DC bus 2, and the DC standby bus. TR3 powers the battery bus and serves as a backup power source for TR1 and TR2. 6.60.10.8 - 20 DEC 13 |
|
|
The cross bus tie relay automatically opens, isolating DC bus 1 from DC bus 2, under the following conditions:
|
• At glideslope capture during a flight director or autopilot ILS approach. This
isolates the DC busses during approach to prevent a single failure from affecting both navigation receivers and flight control computers. • Bus transfer switch positioned to OFF. 6.60.10.8 - 20 DEC 13 |
|
|
How long can a fully charged batteryprovide Standby Power?
|
30 minutes.
6.60.10.8 - 20 DEC 13 |
|
|
What is the battery voltage range?
|
22-30 volts
6.60.10.8 - 20 DEC 13 |
|
|
Which DC busses are powered by the battery following the loss of both generators?
|
• Battery bus
• DC standby bus • Hot battery bus • Switched hot battery bus 6.60.10.8 - 20 DEC 13 |
|
|
When is the Switched Hot Battery Bus powered?
|
Whenever the battery switch is on.
6.60.10.8 - 20 DEC 13 |
|
|
illuminated amber BAT DISCHARGE indicates:
|
Excessive battery discharge is detected.
6.60.10.8 - 20 DEC 13 |
|
|
What is the purpose of the battery charger?
|
To restore and maintain the battery at full electrical power. The battery charger is powered through AC ground service bus 2.
6.60.10.9 - 20 DEC 13 |
|
|
What is the function of the battery charger following completion of the primary charge cycle?
|
It powers loads connected to the hot battery bus and the switched hot battery bus. The battery charger TR also powers the battery bus if TR3 fails. With loss of AC transfer bus 1 or the source of power to DC bus 1, the AC and DC standby busses are powered by the battery/battery charger.
6.60.10.9 - 20 DEC 13 |
|
|
What is the function of the Standby Power System?
|
The standby system provides 115V AC and 24V DC power to essential systems
in the event of loss of all engine or APU-driven AC power. 6.60.10.11 - 20 DEC 13 |
|
|
What are the components of the Standby Power System?
|
• Static inverter
• AC standby bus • DC standby bus • Battery bus • Hot battery bus • Switched hot battery bus • Main battery 6.60.10.11 - 20 DEC 13 |
|
|
How are the following components normally powered?
- AC Standby Bus - DC Standby Bus - Battery Bus - Switched Hot Battery Bus & Hot Battery Bus |
- AC Standby Bus = AC Transfer Bus 1
- DC Standby Bus = TR 1,2 & 3 - Battery Bus = TR3 - Switched Hot Battery Bus & Hot Battery Bus = battery/battery charger. 6.60.10.11 - 20 DEC 13 |
|
|
What is the alternate source of power for the Standby System?
|
The battery.
6.60.10.11 - 20 DEC 13 |
|
|
How are the following components powered during Standby System operation?
- AC Standby Bus - DC Standby Bus - Battery Bus - Switched Hot Battery Bus & Hot Battery Bus |
- AC Standby Bus = Battery via static inverter
- DC Standby Bus = battery - Battery Bus = battery - Switched Hot Battery Bus & Hot Battery Bus = battery 6.60.10.11 - 20 DEC 13 |
|
|
With the Standby Power switch in AUTO, when does automatic switching from normal to alternate power occur?
|
If power from either AC transfer bus 1 or DC bus 1 is lost.
6.60.10.11 - 20 DEC 13 |
|
|
What occurs when the Standby Power Switch is placed to BAT?
|
Automatic switching is overridden and the AC
standby bus, DC standby bus, and battery bus are placed on battery power. Note - The battery switch may be ON or OFF. If the battery switch is OFF, the switched hot battery bus is not powered. 6.60.10.11 - 20 DEC 13 |
|
|
What occurs when the Standby Power Switch is positioned to OFF?
|
Both the AC standby bus and the DC standby bus are de-energized and the STANDBY PWR OFF light is illuminated.
6.60.10.11 - 20 DEC 13 |
|
|
What is the purpose of the static inverter?
|
Converts 24 volt DC power from the battery to 115V AC power
to supply the AC standby bus during the loss of normal electrical power. |
