What is the role of the rotating armature in a DC generator?

To generate electrical energy by rotating within a magnetic field

To maintain constant voltage output

What is the purpose of the brush assembly in a DC generator?

To transfer electrical current from the rotating armature to the external circuit

To cool down the generator during operation

What is one of the primary functions of the field frame in a DC generator?

To hold the windings that produce the magnetic field

In a series-wound DC generator, what happens to the output voltage when the aircraft electrical load is increased?

The output voltage remains constant

What is the primary reason series-wound generators have poor voltage regulation?

The field winding is connected in series with the external circuit

They have no connection to the external circuit

The field winding is connected in parallel with the external circuit

What determines the type of DC generator to be used in an aircraft?

The connection of the armature and field circuits with respect to the external circuit

The speed of the armature rotation

The material used for the commutator segments

What should be checked if oil is present in the generator during maintenance?

Engine oil seals and clean dirt with compressed air

The generator's power output and voltage regulation

The commutator segments for wear and tear

What is the importance of inspecting the condition of generator brushes during maintenance?

To ensure they are making proper contact with the commutator and to check for excessive wear or sparking

To verify the generator's rotational speed

To adjust the generator's output voltage

What is the correct procedure for sanding brushes to improve contact with slip rings or commutators?

Sand in the direction of armature rotation with extra-fine sandpaper, keeping the brush elevated when pulling back

Sand the brush in any direction, and use emery cloth for better results

Use coarse sandpaper and sand the brush perpendicular to the direction of armature rotation

How does the strength of the magnetic field in a DC generator affect the output voltage?

A stronger magnetic field results in higher output voltage

A stronger magnetic field results in lower output voltage

The magnetic field strength has no effect on the output voltage

According to Fleming's right-hand rule, what happens when the direction of armature rotation is reversed in a DC generator?

The direction of the induced current is reversed

The direction of the induced current remains unchanged

When a coil with current flowing through it is placed in a magnetic field, what happens to the coil if current flows inward on one side and outward on the other?

The coil will rotate until its plane is perpendicular to the magnetic lines.

The coil will not rotate and remain stationary.

The coil will rotate until its plane is parallel to the magnetic lines.

In the context of a current-carrying coil in a magnetic field, what causes side A of the coil to move upward while side B moves downward?

The counter-clockwise magnetic field around side A and clockwise around side B.

The clockwise magnetic field around side A and counter-clockwise around side B.

The fields in both sides of the coil are neutral, causing no movement.

How does the coil's rotation orientation relate to the magnetic lines of force in a magnetic field?

The coil rotates until it is perpendicular to the magnetic lines of force.

The coil rotates until it is parallel to the magnetic lines of force.

The coil continues to rotate in any direction regardless of the magnetic lines of force.

How does the torque on the coil change when the coil rotates from Position A to Position B, where the coil is at a 90° angle to the original position?

Torque reaches a maximum at Position A and a minimum at Position B.

Torque remains constant throughout the rotation.

What material is commonly used for the brushes in a DC motor, and why?

Graphitic carbon, due to its long service life and minimal wear to the commutator.

Copper, for its excellent electrical conductivity.

Silver, for its superior conductivity and durability.

What happens if the load is removed entirely from a series DC motor?

The motor may operate at dangerously high speeds, potentially damaging the armature.

The motor operates at a slower, safer speed.

In which applications are series DC motors commonly used in aircraft?

For engine starters and raising and lowering landing gear and flaps.

For controlling cockpit instruments.

For high-speed, low-load applications.

How is the field winding of a shunt motor connected?

In parallel with the armature winding.

In series with the armature winding.

In series with the power supply.

What is the effect of high resistance in the field winding of a shunt motor?

It allows the field current to remain constant.

It causes the field current to vary with motor speed.

It reduces the overall efficiency of the motor.

Why does a shunt motor produce less starting torque compared to a series motor?

Because the field current is constant and does not vary with motor speed.

Because the field winding is connected directly across the power supply.

Because the motor speed is proportional to load.

How does the speed of a shunt motor respond to changes in load?

The speed varies very little with changes in load.

The speed decreases significantly with increasing load.

The speed increases significantly when the load decreases.

What type of motor operation is characterized by the need for cooling periods after short runs?

Both continuous and intermittent duty motors.

What is a split field motor?

A motor with two field windings wound in opposite directions on the same pole.

A motor with two field windings wound in the same direction.

How can the speed of a DC motor be controlled?

By varying the current in the field windings.

By changing the resistance in the armature windings.

What happens when the current through the field windings is increased?

The motor slows down as the counter EMF increases.

The motor speeds up as the counter EMF decreases.

The motor runs at constant speed.

How does the rheostat control motor speed in a shunt motor?

By increasing or decreasing resistance, which changes the field current and, thus, the motor speed.

By varying the current in the armature windings.

By altering the voltage applied to the armature.

When a DC motor exhibits chattering of the relay switch, what is the most probable cause?

Low battery causing insufficient voltage to hold the relay

High mica insulation on commutator

Faulty commutator causing arcing

What is the typical voltage and peak amperage required for starting with a starter generator system?

24 volts and 1,500 peak amperes

12 volts and 1,000 peak amperes

What is a key operational difference between a starter generator unit and a direct cranking starter in terms of their engagement with the engine shaft?

Starter generator is permanently engaged with the shaft

Direct cranking starter is permanently engaged

Starter generator requires manual engagement

3.12 DC Motor Generator

Authored by Rajendra Singh Chundawat

Engineering

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40 questions

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MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What factor primarily determines the strength of the voltage induced in the conductor of a generator?

The length of the conductor

The speed of the conductor's movement within the magnetic field

The thickness of the conductor

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

When the loop in a simple generator is parallel to the magnetic lines of force, why is the induced voltage zero?

The loop is cutting the lines of force at maximum rate

The loop is not cutting any magnetic lines of force

The magnetic field cancels out the voltage

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

How does armature reaction affect the brush position on the commutator?

It causes the brushes to wear out faster

It shifts the main field poles without a corresponding shift in brush positions

It stabilizes the brush positions

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What happens to the output voltage of a DC generator as the number of loops in the rotor is increased?

The variation between maximum and minimum voltage values is reduced

The output voltage varies more widely

The output voltage becomes more unstable

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

How does armature reaction change with increasing generator load?

Armature reaction decreases

Armature reaction remains constant

Armature reaction increases

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is one potential effect of armature reaction that directly impacts the commutator?

Brush sparking on the commutator

Increased commutator wear

Enhanced commutator efficiency

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Why do DC generators require a control circuit?

To ensure the generator maintains the correct voltage and current

To control the rotational speed of the armature

To monitor the temperature of the generator

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3.12 DC Motor Generator

What factor primarily determines the strength of the voltage induced in the conductor of a generator?

When the loop in a simple generator is parallel to the magnetic lines of force, why is the induced voltage zero?

How does armature reaction affect the brush position on the commutator?

What happens to the output voltage of a DC generator as the number of loops in the rotor is increased?

How does armature reaction change with increasing generator load?

What is one potential effect of armature reaction that directly impacts the commutator?

Why do DC generators require a control circuit?

Which of the following is NOT a major component of a DC generator?

What is the role of the rotating armature in a DC generator?

What is the purpose of the brush assembly in a DC generator?

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