All non-failure AC power transfers are No-Break Power Transfer (NBPT), except between external AC power and APU power sources.
When the BPCUs transfer main AC buses to available power sources, the BPCUs first ensure that the power source parameters match in terms of frequency and phase angle. The BPCUs select one of the power sources as a reference for comparison, then signals the GCU to adjust IDG frequency and/or phase angle so that both power sources are congruent. This process is termed 'paralleling' and enables the BPCU to achieve a No-Break Power Transfer (NBPT) that maintains power on the buses while switching power sources. All automatic power transfers will be NBPTs except those between an external AC power source and the APU generator, since the APU generator is not an IDG and the GCU cannot adjust frequency or phase angle without a hydro-mechanical drive unit.
When airspeed falls below the limit of RAT operation, RAT stops operating and Main, Uninterruptable Power System (UPS) and Electrical Backup Hydraulic Actuators (EBHA) batteries begin to power flight critical systems for up to _____.
How are emergency batteries activated?
The Emergency Batteries (FWD and AFT), provide redundant, uninterruptable power to L and R Emergency Busses as well as to the Flight Instrument Bus.
One is located up forward in LEER and the other one is located back aft on left side of baggage compartment in Auxiliary EER.
What are the sources of power for ground service bus?
What is the purpose of the Flight Control Uninterruptable Power System (UPS) battery?
When are L and R AUX DC buses load shed?
The batteries have a split bus configuration. Only the right battery is involved in APU start. Both batteries power the AUX pump.
Only the left battery is involved in APU start. Both batteries power the AUX pump.
What are the sources of power for ground service bus?
The minimum airspeed for RAT operation is approximately:
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ON / OFF control and reset of the APU generator (and its output contactor) is provided by the APU GEN switch located in the Cockpit Overhead Panel (COP). A 'Ready to Load' signal from the APU Ready to Load relay permits the Generator Control Unit (GCU) to energize the Auxiliary AC Contactor (AAC) once the APU has reached _____.
The Ground Service Bus (GSB) is provided for normal aircraft servicing without activation of external power or operation of the APU or engines. Power for the GSB is supplied by the _____.
If all sources of power are lost, how many minutes will emergency batteries provide electrical power to the left and right emergency DC buses, essential flight instrument bus, and inertial reference units to support equipment essential for safety of flight as well as emergency lighting?
How are emergency batteries activated?
What is the minimum battery voltage required during cockpit preflight inspection?
When would MAIN BATTERY switches indicate amber ON?
On ground, the right battery is used to power the ground service bus when not powered by the right main DC bus or external DC power.
The LEFT battery is used to power ground service bus when not powered by the right main DC bus or external DC power.
DC power for essential flight functions is furnished by the two 53 Amp/Hour aircraft batteries, designated as 'Main Batteries'.
How can a Generator Control Unit (GCU) be reset?
This action causes the software to re-initialize.
The IDGs are rated at 40 kVA and provide three-phase, 400 Hz, 115 VAC power.
A constant rotational speed enables the GCU to maintain AC power parameters of 3-phase 115/200V AC at 400 cycles-per-second (Hz) and deliver up to 40,000 volt / amps (40 kVA).
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If all sources of power are lost, how many minutes will emergency batteries provide electrical power to the left and right emergency DC buses, essential flight instrument bus, and inertial reference units to support equipment essential for safety of flight as well as emergency lighting?
What are main battery charging requirements?
_____ the Emergency AC bus during normal operation.
The battery/charger TR mode is initiated when battery switches are selected ON, main AC buses are powered, and the following occur - APU start switch is selected ON, aux pump is turned on, or essential DC buses require power from batteries.
Electrical Power Control Panel - If both AC and DC external power are available at the same time, the AVAIL legend will remain illuminated to indicate DC external power is still available although AC external power has been selected.
The IDG rotates whenever the engine is operating. Under normal operating conditions, there is no provision for disconnecting the IDG from the engine while in flight, however; a thermal disconnect will decouple the engine reduction gearbox rotational power from the IDG in the event of a _____.
Left and right bus tie switches on the cockpit overhead panel can prevent a bus from receiving power from another generator source. Selecting the R BUS TIE or L BUS TIE switches to ISLN (isolation) allows only the respective right or left engine IDG to power the associated bus.
AC electrical power is distributed throughout the aircraft by the following buses:
When should you remove the batteries?
If the main airplane batteries will be exposed to temperature below -20 deg.C (0 deg.F), the batteries should be removed and stored in an area warmer than -20 deg.C (0 deg.F), but below +40 deg.C (104 deg.F).
What is the function of the Electrical Backup Hydraulic Actuators (EBHA) battery?
The Motor Control Electronics (MCE) is used to control the EBHA electric motor-pump when the actuator is in the Electric Backup state due to hydraulic or Remote Electronics Unit (REU) failures. If an EBHA is in the normal hydraulically active state, the Motor Control Electronics (MCE) is in a standby condition wherein it still processes commands and sends them back to the Flight Control Computers (FCCs) through its REU to monitor its availability.
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The GCUs will de-energize the associated generator if a _____
What causes 'DC' legend of AC/DC RESET switch light to activate?
What is the rating of the RAT?
On a dark airplane, what occurs when EXTERNAL BATTERY switch is selected to ON?
Load shed feature is available both on ground and in flight.
Load shed feature is inhibited on ground.
RAT deployment can be automatic or manual depending on the situation.
Deployment of the RAT is by manual means (handle/cable) only.
What is the difference between red and black circuit breakers?
The Emergency Batteries (FWD and AFT), provide redundant, uninterruptable power to L and R Emergency Busses as well as to the Flight Instrument Bus.
One is located up forward in LEER and the other one is located back aft on left side of baggage compartment in Auxiliary EER.