NAVEDTRA 14177A, NEETS, MODULE 05 -- GENERATORS AND MOTORS

In a two-phase motor stator, what is the angular displacement between the field poles?



• 
0º

• 
180º

• 
90º
• 
360º

Under which of the following conditions does sparking occur between the brushes and the commutator?



• 
When operating under normal conditions

• 
When there is an excessive load current

• 
When commutation is in the neutral plane (your response)

• 
When there is improper commutation

Which of the following is NOT a major classification of dc generators?



• 
Lap-wound (correct answer)

• 
Series-wound

• 
Compound-wound
• 
Shunt-wound

What special-purpose dc generator is used as a high-gain power amplifier?



• 
Amplidyne 

• 
Shunt-wound

• 
Lap-wound

• 
Compound-connected

The current in the interpoles of a dc motor is the same as the



• 
eddy current

• 
field current

• 
armature current 

• 
total load current

How can the direction of rotation be changed in a dc motor?



• 
Only by reversing the field connections

• 
By reversing both the armature connections and the field connections

• 
Only by reversing the armature connections

• 
By reversing either the armature connections or the field connections

The ac power aboard ship is usually distributed as what voltage?



• 
115-volt, three-phase

• 
230-volt, single-phase

• 
115-volt, single-phase

• 
450-volt, three-phase

In alternators with low-speed prime movers, only what type of rotor may be used?



• 
Armature

• 
Turbine-driven

• 
Geared

• 
Salient-pole

What does the term single-phase mean relative to single-phase alternators?



• 
Only one voltage is produced 

• 
The voltage and current are in phase

• 
All output voltages are in phase with each other

• 
The phase angle is constant

Eddy currents in armature cores are kept low by which of the following actions?



• 
Using powdered iron as a core material

• 
Laminating the iron in the core
• 
Insulating the core

• 
Limiting armature current

What term applies to the difference between the speed of the rotating stator field and the rotor speed?



• 
Slip
• 
Rotor error

• 
Torque

• 
Synchronous

What determines the direction of rotation of a dc motor?



• 
The number of armature coils

• 
The method of excitation

• 
The polarity of armature current and direction of magnetic flux 

• 
The type of armature

What is the load on a dc motor?



• 
The total current drawn from the source

• 
The armature current

• 
The field current

• 
The mechanical device the motor moves

When a series dc motor is operated without a load, which of the following conditions occurs?



• 
The armature draws excessive current

• 
The armature will not turn

• 
The armature speeds out of control

• 
The voltage requirement increases

Magnetic induction in an alternator is a result of relative motion between what two elements?



• 
The field and the stator

• 
The armature and the field 

• 
The rotor and the field

• 
The rotor and the armature

When two adjacent segments of the commutator on a single-loop dc generator come in contact with the brush at the same time, which of the following conditions will occur?



• 
The output voltage will be zero
• 
The output voltage will be maximum negative

• 
The output voltage will be maximum positive

What type of ac motor is the simplest and least expensive to manufacture?



• 
Synchronous

• 
Two-phase

•  

Induction
• 
Series

In a single-phase alternator with multiple armature windings, how must the windings be connected?



• 
Parallel

• 
Delta

• 
Series 

• 
Wye

When you use the left-hand rule for generators, what is indicated by the middle finger?



• 
Direction of the magnetic field

• 
Direction of flux

• 
Direction of current flow 

• 
Direction of motion

In a dc motor, what causes counter emf?



• 
Improper commutation

• 
Generator action
• 
Excessive speed

• 
Armature reaction

In generators, what principle is used to convert mechanical motion to electrical energy?



• 
Magnetic repulsion

• 
Atomic reaction

• 
Magnetic induction

• 
Electrical attraction

Distortion of the main field by interaction with the armature field can be compensated for by the use of



• 
slip rings

• 
interpoles 

• 
special brushes

• 
a commutator

In most alternators, the output voltage is controlled by adjusting the



• 
rotor speed

• 
electric load

• 
field voltage

• 
armature resistance

In an elementary, single-coil, dc generator with one pair of poles, what is the maximum number of pulsations produced in one revolution?



• 
One

• 
Two 

• 
Three

• 
Four

Adjacent phase windings of a 3-phase motor stator are what total number of degrees apart?



• 
90º

• 
30º

• 
120º 

• 
180º

In a dc motor, the neutral plane shifts in what direction as the result of armature reaction?



• 
Opposite the direction of rotation

• 
Counterclockwise

• 
Clockwise

• 
In the direction of rotation

The number of pole pairs required to establish a rotating magnetic field in a multiphase motor stator is determined by which of the following factors?



• 
The magnitude of the voltage

• 
The magnitude of the current

• 
The size of the motor

• 
The number of phases

What components cause(s) a generator to produce a dc voltage instead of an ac voltage at its output?



• 
The brushes

• 
The commutator
• 
The armature

• 
The slip rings

Which, if any, of the following situations is a major electrical difference between a dc motor and a dc generator?



• 
The armatures are different

• 
The shunt connections are different

• 
The dc generator requires a commutator, the dc motor does not

• 
None of the above

What type of ac motor is most widely used?



• 
Series

• 
Universal

• 
Synchronous

• 
Single-phase induction

The maximum gain possible from an amplidyne is approximately



• 
10,000 

• 
50,000

• 
100

• 
5,000

Which of the following types of motors is widely used to power small appliances?



• 
Compound

• 
Universal

• 
Synchronous

• 
Polyphase

A universal motor is a special type of



• 
series motor 

• 
parallel motor

• 
synchronous motor

• 
polyphase motor

Which of the following types of motors has a constant speed from no load to full load?



• 
Universal

• 
Synchronous 

• 
Induction

• 
Series

How can you vary the strength of the magnetic field in a dc generator?



• 
By varying the speed of armature rotation

• 
By varying the voltage applied to the electromagnetic field coils 

• 
By varying the armature current

• 
By varying the polarity of the field poles

What type of dc generator application best utilizes the features of the lapwound armature?



• 
High-voltage

• 
High-current 

• 
High-speed

• 
Variable-speed

When you use the right-hand rule for motors, what quantity is indicated by the extended forefinger?



• 
Direction of motion

• 
Direction of current

• 
Direction of flux south to north

• 
Direction of flux north to south

The speed of the rotor of an induction motor depends upon which of the following factors?



• 
The method of connecting the load

• 
The torque requirements of the load 

• 
The current in the rotor

• 
The dc voltage applied to the rotor

The output frequency of an alternator is determined by what two factors?



• 
The number of poles and the number of phases

• 
The speed of rotation and the voltampere rating

• 
The number of phases and the voltampere rating

• 
The number of poles and the speed of rotation

In a dc motor, what is the purpose of the resistor placed in series with the armature?



• 
To prevent overspeeding

• 
To increase field strength

• 
To counteract armature reaction

• 
To limit armature current

Alternators are rated using which of the following terms?



• 
Amperes

• 
Volts
• 
Volt-amperes

• 
Watts

Distortion of the main field by interaction with the armature field defines what term?



• 
Mutual induction

• 
Mutual reaction

• 
Armature reaction

• 
Commutation

As the load current of a dc generator varies from no-load to full-load, the variation in output voltage is expressed as a percent of the full-load voltage. What term applies to this expression?



• 
Load limit

• 
Voltage regulation

• 
Voltage control

• 
Gain

What characteristic of series-wound generators makes them unsuitable for most applications?



• 
They are not capable of supplying heavy loads

• 
They require external field excitation

• 
The output voltage varies as the load current varies 

• 
The output voltage varies as the speed varies

A dc series motor is best suited for which of the following applications?



• 
Steady load, high torque

• 
Variable load, high torque 

• 
Variable load, low torque

• 
Steady load, low torque

When two or more generators are used to supply a common load, what term is applied to this method of operation?



• 
Series

• 
Split-load

• 
Compound

• 
Parallel

Why are shaded-pole motors built only in small sizes?



• 
They have weak starting torque

• 
They require large starting current

• 
They are unidirectional

• 
They are expensive in large sizes

When the voltage applied to the armature of a dc shunt motor is decreased, what happens to the motor speed?



• 
It increases

• 
It decreases

• 
The motor stops

• 
It becomes uncontrollable

In a dc motor, how, if at all, does counter emf affect speed?



• 
It causes the speed to decrease

• 
It does not affect speed 

• 
It causes the speed to increase

• 
It causes rapid fluctuations of the speed

An elementary generator consists of a single coil rotating in a magnetic field. Why is NO voltage induced in the coil as it passes through the neutral plane?



• 
Flux lines are too dense

• 
Flux lines are not being cut 

• 
Flux lines are not present

• 
Flux lines are being cut in the wrong direction

What are the two basic types of alternators?



• 
Multiphase and polyphase

• 
Alternating current and direct current

• 
Series-wound and shunt-wound

• 
Rotating field and rotating armature

The gain of an amplifying device can be determined by which of the following formulas?



• 
GAIN = OUTPUT / INPUT
• 
GAIN = OUTPUT- INPUT

• 
GAIN = INPUT + OUTPUT

• 
GAIN = INPUT *OUTPUT

The output voltage of an elementary generator is coupled from the armature to the brushes by what devices?



• 
Interpoles

• 
Terminals

• 
Pigtails

• 
Slip rings

Voltage is induced in what part of an alternator?



• 
The brushes

• 
The armature

• 
The field

• 
The commutator

An alternator using a gas turbine as a prime mover should have what type of rotor?



• 
Armature

• 
Geared

• 
Turbine-driven

• 
Salient-pole

What is the main advantage of a shunt motor over a series motor?



• 
A shunt motor draws less current from the source than a series motor

• 
A shunt motor develops higher torque at lower speeds than a series motor

• 
A shunt motor maintains a more constant speed under varying load conditions than a series motor

• 
A shunt motor can be operated at higher speeds than a series motor

What is the phase relationship between the output voltages of a three-phase alternator?



• 
In phase

• 
120ºout of phase

• 
90ºout of phase

• 
60ºout of phase

Motor reaction in a dc generator is a physical force caused by the magnetic interaction between the armature and the field. What effect, if any, does this force have on the operation of the generator?



• 
It tends to oppose the rotation of the armature 

• 
It tends to aid the rotation of the armature

• 
It causes the generator to vibrate

• 
None

What type of ac motor uses a combination of inductance and capacitance to apply out-of-phase currents to the start windings?



• 
Synchronous

• 
Series

• 
Split-phase induction

• 
Three-phase

Which of the following motors is/are types of ac motor?



• 
Series

• 
Synchronous

• 
Induction

• 
All of the above