30 Questions
What type of generators are used as the principal source of electric power in almost all transport-category aircraft?
AC generators
What is used to produce a DC output in a DC alternator?
Internal rectifiers
Why are AC generators requiring a constant-speed drive considered too heavy for light aircraft?
They are too heavy
In larger aircraft, what is used to change the engine-driven AC-generated 115-V AC to 28-V DC?
Transformer Rectifier Units (TRUs)
What serves as the backup DC source if other sources do not operate in an aircraft?
Batteries
What is the main difference between the electrical system of light aircraft and that of larger aircraft?
Use of AC generators vs DC alternators
What is the purpose of a tap in a transformer?
To provide a connection at a specific point on the winding
Which component is typically used in rectifier circuits to allow current flow in only one direction?
Diode
What is the primary function of a Transformer Rectifier Unit (TRU)?
Providing continuous DC output from a three-phase AC input
In a rectifier circuit, what is the purpose of converting AC to DC?
To ensure unidirectional current flow
What is one of the reasons for having multiple secondaries or tappings in a transformer?
To provide various voltages higher and lower than the supply voltage
How does a tap in a transformer affect the voltage output?
It varies the voltage based on the tap location
What is the purpose of a Constant Speed Drive (CSD) in an aircraft electrical power system?
To maintain a constant output frequency for AC generators
Which type of generators are typically used in most aircraft applications?
Three-phase alternators
What type of AC power do the generators supply in a turbine-powered aircraft?
Three-phase, 115 V at 400 Hz
In emergency situations, which devices are often used to drive AC generators on aircraft?
Auxiliary Power Units (APUs) or Ram Air Turbines (RATs)
What is a common feature of most AC power systems compared to DC systems in aircraft?
They need a constant-speed drive to maintain frequency
What technology is commonly integrated into one unit in modern aircraft instead of using separate Constant Speed Drives and generators?
Integrated Drive Generator (IDG)
What is the role of the current coil in the relay described in the text?
Assists in keeping the pilot contacts closed
How does the relay ensure the generator is disconnected from the battery during engine shut-down?
By decreasing the generator output voltage
Why are reverse current circuit breakers designed to remain in a 'locked-out' condition?
To protect against fault currents greater than normal cut-out levels
What happens when a fault current greater than normal occurs in a power supply system protected by reverse current circuit breakers?
The circuit breaker locks out to isolate the circuit
How does the relay prevent generator overloading in the system described?
By maintaining a regulated value for the voltage output
What is the consequence of the magnetic effect of the current coil opposing that of the voltage coil during engine shut-down?
The auxiliary and main contacts open to disconnect the generator
What is the primary reason for circuit breakers and fuses to be located close to the power supply?
To prevent short circuits that could lead to overloads and fires
What does a small white band on a circuit breaker indicate?
That the circuit breaker has been tripped
What is a trip-free circuit breaker designed to do?
Immediately open the circuit even when held in the on position
When is a non-trip-free circuit breaker used?
For required control circuits
Which type of circuit breaker can be bypassed by holding the operating mechanism on?
Non-trip-free circuit breaker
Where are trip-free circuit breakers typically used?
On precision or current-sensitive circuits
Test your knowledge on DC power generation in light aircraft. Learn about the use of DC alternators to produce electric power and their advantages over AC generators requiring a constant-speed drive.
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