Master DC Motor Troubleshooting: Techniques and Common Faults

Question 1

Which troubleshooting technique involves measuring voltage drop across components?

Accepted Answer

Voltage drop test

Answer

Visual inspection

Answer

Insulation resistance test

Answer

Ohmmeter test

Question 2

What is the main purpose of the commutator in a DC motor?

Accepted Answer

To reverse current direction

Answer

To convert AC to DC

Answer

To minimize sparking

Answer

To increase motor speed

Question 3

In a series-wound DC motor, the field coils are:

Accepted Answer

Connected in series with the armature

Answer

Connected in parallel with the armature

Answer

Connected in parallel with the power source

Answer

Connected in series with the power source

Question 4

Which type of brush is commonly used in DC motors?

Accepted Answer

Carbon brushes

Answer

Copper brushes

Answer

Steel brushes

Answer

Ceramic brushes

Question 5

What is the function of a fuse in a DC motor circuit?

Accepted Answer

To protect the motor from overcurrent

Answer

To provide a current path

Answer

To regulate motor speed

Answer

To reduce sparking

Question 6

When using an ohmmeter to test for a short circuit in a DC motor armature, what reading indicates a short?

Accepted Answer

Low resistance

Answer

High resistance

Answer

Infinite resistance

Answer

Fluctuating resistance

Question 7

In DC motor troubleshooting, which symptom typically indicates a faulty armature winding?

Accepted Answer

High current draw and motor fails to start

Answer

Reduced motor speed

Answer

Loud humming noise during operation

Answer

Overheating during normal operation

Question 8

When troubleshooting a DC motor, which safety gear is essential for personal protection?

Accepted Answer

Gloves and safety glasses

Answer

Rubber boots and hard hat

Answer

Ear plugs and dust mask

Answer

Fire extinguisher and first aid kit

Question 9

What is the purpose of a shunt field in a DC motor?

Accepted Answer

To regulate the current flow

Answer

To increase the starting torque

Answer

To reduce the speed of the motor

Answer

To reverse the direction of rotation

Question 10

What is the primary function of a starter in a DC motor?

Accepted Answer

To limit the starting current

Answer

To increase the starting torque

Answer

To reverse the direction of rotation

Answer

To provide overcurrent protection

Question 11

What is the main function of a series field in a DC motor?

Accepted Answer

To increase the starting torque

Answer

To reduce the speed of the motor

Answer

To control the current flow

Answer

To reverse the direction of rotation

Question 12

What is the purpose of a commutator in a DC motor?

Accepted Answer

To reverse the current flow in the armature

Answer

To provide a path for the field current

Answer

To connect the armature windings to the external circuit

Answer

To control the speed of the motor

Question 13

How does increased temperature affect a DC motor's performance?

Accepted Answer

Increased resistance leads to slower motor speed.

Answer

Decreased resistance leads to faster motor speed.

Answer

Temperature has no significant impact on motor performance.

Answer

Increased resistance leads to faster motor speed.

Question 14

Which of the following is typically NOT a starting problem experienced in DC motors?

Accepted Answer

Excessive load on the motor

Answer

Open armature circuit

Answer

Short circuit in the field windings

Answer

Weak field magnetism

Question 15

What is the role of brushes in a DC motor?

Accepted Answer

To collect current from the commutator

Answer

To provide electrical insulation between the armature and the field windings

Answer

To regulate the speed of the motor

Answer

To reverse the direction of motor rotation

Question 16

Which tool is typically used to measure armature current in a DC motor?

Accepted Answer

Ammeter

Answer

Voltmeter

Answer

Ohmmeter

Answer

Multimeter

Question 17

In a DC motor, what is the main function of the armature?

Accepted Answer

Generate torque and enable motion

Answer

Regulate motor speed

Answer

Store electrical energy

Question 18

Which of the following is NOT a type of DC motor?

Accepted Answer

Induction motor

Answer

Brush DC motor

Answer

Brushless DC motor

Answer

Permanent magnet DC motor

Question 19

What type of fault would cause a DC motor to run in the opposite direction?

Accepted Answer

Reversed polarity of field or armature connections

Answer

Shorted field winding

Answer

Open armature winding

Answer

Worn bearings

Question 20

What instrument is used to measure the resistance of a DC motor's armature winding?

Accepted Answer

Multimeter

Answer

Ammeter

Answer

Voltmeter

Answer

Tachometer

Question 21

What is the purpose of the field winding in a DC motor?

Accepted Answer

To create a magnetic field

Answer

To generate voltage

Answer

To provide mechanical support

Answer

To carry the armature current

Question 22

Which of the following is a common symptom of an open armature circuit in a DC motor?

Accepted Answer

Motor fails to start

Answer

Motor sparks excessively

Answer

Motor runs erratically

Answer

Motor overheats

Question 23

What is the primary purpose of using a voltmeter when troubleshooting DC motors?

Accepted Answer

To measure voltage drops and identify potential faults

Answer

To determine the speed of the motor

Answer

To check the current flow

Question 24

When troubleshooting DC motors, what is the initial step recommended for electricians?

Accepted Answer

Inspect the motor visually for any obvious faults

Answer

Measure the resistance of the armature windings

Answer

Apply voltage to the motor and observe its behavior

Answer

Check the insulation of the windings

Question 25

Which type of DC motor connection is NOT commonly used?

Accepted Answer

Delta connection

Answer

Shunt connection

Answer

Series connection

Answer

Compound connection

Question 26

What is the primary function of the commutator in a DC motor?

Accepted Answer

To reverse the direction of current flow in the armature windings

Answer

To provide mechanical support for the armature

Answer

To increase the voltage of the motor

Question 27

What is the primary purpose of using a growler during DC motor troubleshooting?

Accepted Answer

To detect shorted or open windings in the stator

Answer

To identify loose connections

Answer

To measure the current flow in the motor

Question 28

Which of the following factors is crucial when choosing test equipment for DC motor troubleshooting?

Accepted Answer

Appropriate voltage and current ranges

Answer

Color and design

Answer

Brand and manufacturer

Answer

Price and availability

Question 29

When troubleshooting a DC motor that is not running, the most appropriate initial step is to:

Accepted Answer

Check for power supply

Answer

Inspect the field windings

Answer

Test the armature resistance

Answer

Measure the field current

Question 30

Select the tool that is most suitable for measuring the armature resistance of a DC motor:

Accepted Answer

Ohmmeter

Answer

Voltmeter

Answer

Ammeter

Answer

Capacitance meter

Question 31

A humming sound emitted by a DC motor typically indicates:

Accepted Answer

Shorted armature coils

Answer

Open field winding

Answer

Loose bearings

Answer

Misaligned brushes

Question 32

To ensure effective troubleshooting of DC motors, it is essential to:

Accepted Answer

Follow a systematic and logical approach

Answer

Rely solely on experience without following a structured process

Answer

Ignore safety precautions and work in hazardous conditions

Answer

Guess and replace components randomly